[r|d]/aws_memorydb_user(test): adjust iam authentication_mode tests

Simplifies the configuration by removing tags (tested in other
configurations) and applies consistent naming to both tests and
associated configurations.

```console
% make testacc PKG=memorydb TESTS="TestAccMemoryDBUser|TestAccMemoryDBUserDataSource"
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go1.22.2 test ./internal/service/memorydb/... -v -count 1 -parallel 20 -run='TestAccMemoryDBUser|TestAccMemoryDBUserDataSource'  -timeout 360m

--- PASS: TestAccMemoryDBUser_tags (45.96s)
--- PASS: TestAccMemoryDBUserDataSource_authenticationModeIAM (49.38s)
--- PASS: TestAccMemoryDBUserDataSource_basic (49.38s)
--- PASS: TestAccMemoryDBUser_basic (52.16s)
--- PASS: TestAccMemoryDBUser_authenticationModeIAM (52.20s)
--- PASS: TestAccMemoryDBUser_disappears (58.02s)
--- PASS: TestAccMemoryDBUser_update_accessString (105.60s)
--- PASS: TestAccMemoryDBUser_update_passwords (173.49s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/memorydb   178.422s
```

internal/service/memorydb/user_data_source_test.go

@@ -41,7 +41,7 @@ func TestAccMemoryDBUserDataSource_basic(t *testing.T) {
 	})
 }
 
-func TestAccMemoryDBUserDataSource_iam(t *testing.T) {
+func TestAccMemoryDBUserDataSource_authenticationModeIAM(t *testing.T) {
 	ctx := acctest.Context(t)
 	rName := "tf-test-" + sdkacctest.RandString(8)
 	resourceName := "aws_memorydb_user.test"
@@ -53,15 +53,13 @@ func TestAccMemoryDBUserDataSource_iam(t *testing.T) {
 		ProtoV5ProviderFactories: acctest.ProtoV5ProviderFactories,
 		Steps: []resource.TestStep{
 			{
-				Config: testAccUserDataSourceConfig_iam(rName),
+				Config: testAccUserDataSourceConfig_authenticationModeIAM(rName),
 				Check: resource.ComposeAggregateTestCheckFunc(
 					resource.TestCheckResourceAttrPair(dataSourceName, "access_string", resourceName, "access_string"),
 					resource.TestCheckResourceAttrPair(dataSourceName, "arn", resourceName, "arn"),
 					resource.TestCheckResourceAttrPair(dataSourceName, "authentication_mode.0.type", resourceName, "authentication_mode.0.type"),
 					resource.TestCheckResourceAttrPair(dataSourceName, "authentication_mode.0.password_count", resourceName, "authentication_mode.0.password_count"),
 					resource.TestCheckResourceAttrPair(dataSourceName, "minimum_engine_version", resourceName, "minimum_engine_version"),
-					resource.TestCheckResourceAttr(dataSourceName, "tags.%", "1"),
-					resource.TestCheckResourceAttrPair(dataSourceName, "tags.Test", resourceName, "tags.Test"),
 					resource.TestCheckResourceAttrPair(dataSourceName, "user_name", resourceName, "user_name"),
 				),
 			},
@@ -91,7 +89,7 @@ data "aws_memorydb_user" "test" {
 `, rName)
 }
 
-func testAccUserDataSourceConfig_iam(rName string) string {
+func testAccUserDataSourceConfig_authenticationModeIAM(rName string) string {
 	return fmt.Sprintf(`
 resource "aws_memorydb_user" "test" {
   access_string = "on ~* &* +@all"
@@ -100,10 +98,6 @@ resource "aws_memorydb_user" "test" {
   authentication_mode {
     type = "iam"
   }
-
-  tags = {
-    Test = "test"
-  }
 }
 
 data "aws_memorydb_user" "test" {

internal/service/memorydb/user_test.go

@@ -55,7 +55,7 @@ func TestAccMemoryDBUser_basic(t *testing.T) {
 	})
 }
 
-func TestAccMemoryDBUser_iam_auth_mode(t *testing.T) {
+func TestAccMemoryDBUser_authenticationModeIAM(t *testing.T) {
 	ctx := acctest.Context(t)
 	rName := "tf-test-" + sdkacctest.RandString(8)
 	resourceName := "aws_memorydb_user.test"
@@ -67,7 +67,7 @@ func TestAccMemoryDBUser_iam_auth_mode(t *testing.T) {
 		CheckDestroy:             testAccCheckUserDestroy(ctx),
 		Steps: []resource.TestStep{
 			{
-				Config: testAccUserConfigWithIAMAuthMode_basic(rName),
+				Config: testAccUserConfig_authenticationModeIAM(rName),
 				Check: resource.ComposeTestCheckFunc(
 					testAccCheckUserExists(ctx, resourceName),
 					resource.TestCheckResourceAttr(resourceName, "access_string", "on ~* &* +@all"),
@@ -76,8 +76,6 @@ func TestAccMemoryDBUser_iam_auth_mode(t *testing.T) {
 					resource.TestCheckResourceAttr(resourceName, "authentication_mode.0.password_count", "0"),
 					resource.TestCheckResourceAttrSet(resourceName, "minimum_engine_version"),
 					resource.TestCheckResourceAttr(resourceName, "user_name", rName),
-					resource.TestCheckResourceAttr(resourceName, "tags.%", "1"),
-					resource.TestCheckResourceAttr(resourceName, "tags.Test", "test"),
 				),
 			},
 			{
@@ -313,7 +311,7 @@ resource "aws_memorydb_user" "test" {
 `, rName)
 }
 
-func testAccUserConfigWithIAMAuthMode_basic(rName string) string {
+func testAccUserConfig_authenticationModeIAM(rName string) string {
 	return fmt.Sprintf(`
 resource "aws_memorydb_user" "test" {
   access_string = "on ~* &* +@all"
@@ -322,10 +320,6 @@ resource "aws_memorydb_user" "test" {
   authentication_mode {
     type = "iam"
   }
-
-  tags = {
-    Test = "test"
-  }
 }
 `, rName)
 }