[ObjC] address review comments in #33590 (#33747)

follow up from #33590

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tools/internal_ci/macos/grpc_objc_bazel_test.sh

@@ -122,16 +122,13 @@ objc_bazel_tests/bazel_wrapper \
 
 
 # Enable event engine and run tests again.
-TEST_TARGETS=(
+EVENT_ENGINE_TEST_TARGETS=(
   //src/objective-c/tests:InteropTestsLocalCleartext
   //src/objective-c/tests:InteropTestsLocalSSL
   //src/objective-c/tests:InteropTestsRemote
   //src/objective-c/tests:MacTests
   //src/objective-c/tests:UnitTests
   //src/objective-c/tests:tvtests_build_test
-  # codegen plugin tests
-  //src/objective-c/tests:objc_codegen_plugin_test
-  //src/objective-c/tests:objc_codegen_plugin_option_test
 )
 
 python3 tools/run_tests/python_utils/bazel_report_helper.py --report_path objc_event_engine_bazel_tests
@@ -148,4 +145,4 @@ objc_event_engine_bazel_tests/bazel_wrapper \
   "${OBJC_TEST_ENV_ARGS[@]}" \
   -- \
   "${EXAMPLE_TARGETS[@]}" \
-  "${TEST_TARGETS[@]}"
+  "${EVENT_ENGINE_TEST_TARGETS[@]}"