update doc due to alpine removal

Signed-off-by: Rui Yang <[email protected]>

README.md

@@ -595,11 +595,10 @@ environment is consistent across any `docker` enabled platform. When the docker
 image builds, the test are run inside the docker container, on failure they
 will stop the build.
 
-Run the tests with the following commands for both `alpine` and `ubuntu` images:
+Run the tests with the following commands:
 
 ```sh
-docker build -t registry-image-resource --target tests -f dockerfiles/alpine/Dockerfile .
-docker build -t registry-image-resource --target tests -f dockerfiles/ubuntu/Dockerfile --build-arg base_image=ubuntu:latest .
+docker build -t registry-image-resource --target tests --build-arg base_image=paketobuildpacks/run-jammy-base:latest .
 
 ```
 
@@ -612,17 +611,7 @@ dockerhub repo, and one GCR repo. The `docker build` step requires setting
 Run the tests with the following command:
 
 ```sh
-docker build . -t registry-image-resource --target tests -f dockerfiles/alpine/Dockerfile \
-  --build-arg DOCKER_PRIVATE_USERNAME="some-username" \
-  --build-arg DOCKER_PRIVATE_PASSWORD="some-password" \
-  --build-arg DOCKER_PRIVATE_REPO="some/repo" \
-  --build-arg DOCKER_PUSH_USERNAME="some-username" \
-  --build-arg DOCKER_PUSH_PASSWORD="some-password" \
-  --build-arg DOCKER_PUSH_REPO="some/repo" \
-  --build-arg GCR_PUSH_SERVICE_ACCOUNT_KEY='{"some":"json"}' \
-  --build-arg GCR_PUSH_REPO="some/repo"
-
-docker build . -t registry-image-resource --target tests -f dockerfiles/ubuntu/Dockerfile \
+docker build . -t registry-image-resource --target tests \
   --build-arg DOCKER_PRIVATE_USERNAME="some-username" \
   --build-arg DOCKER_PRIVATE_PASSWORD="some-password" \
   --build-arg DOCKER_PRIVATE_REPO="some/repo" \