fix: prevent duplicate group test runs in CI matrix

The basic lane's -run "TestIAM" regex also matched TestIAMGroup*
tests, causing them to run in both the basic and group lanes.
Replace with explicit test function names.

.github/workflows/s3-iam-tests.yml

@@ -121,7 +121,7 @@ jobs:
             "basic")
               echo "Running basic IAM functionality tests..."
               make clean setup start-services wait-for-services
-              go test -v -timeout 15m -run "TestS3IAMAuthentication|TestS3IAMBasicWorkflow|TestS3IAMTokenValidation|TestIAM" ./...
+              go test -v -timeout 15m -run "TestS3IAMAuthentication|TestS3IAMBasicWorkflow|TestS3IAMTokenValidation|TestIAMUserManagement|TestIAMAccessKeyManagement|TestIAMPolicyManagement" ./...
               ;;
             "advanced")
               echo "Running advanced IAM feature tests..."