swap tabs for spaces in rickshaw-settings.json

- this allows rickshaw-settings.json to be manipulated with tools such
  as jq and maintain consistency by using 4 space indendation

- consistency is key for seemless merging of upstream changes to the
  file

rickshaw-settings.json

@@ -1,23 +1,23 @@
 {
     "roadblock": {
-	"timeouts": {
-	    "default": 240,
-	    "endpoint-deploy": 1440,
-	    "collect-sysinfo": 1200,
-	    "engine-start": 1440,
-	    "move-data": 300
-	}
+        "timeouts": {
+            "default": 240,
+            "endpoint-deploy": 1440,
+            "collect-sysinfo": 1200,
+            "engine-start": 1440,
+            "move-data": 300
+        }
     },
     "userenvs": {
-	"default": {
-        "benchmarks": "rhubi9",
-	    "tools": "fedora-latest"
+        "default": {
+            "benchmarks": "rhubi9",
+            "tools": "fedora-latest"
         }
     },
     "endpoints": {
-	"default": {
-	    "user": "root"
-	}
+        "default": {
+            "user": "root"
+        }
     },
     "workshop": {
         "force-builds": "false",