V8: Remove gyp-flag-comparison feature after MB switch.

scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux64___gcov_coverage.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "client.v8",
       "--builder",
       "V8 Linux64 - gcov coverage",
@@ skipping 174 matching lines @@
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "generate_build_files",
     "stdout": "/path/to/tmp/",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@stdout@some line@@@",
       "@@@STEP_LOG_LINE@stdout@GYP_DEFINES='target_arch=x64 cool_flag=a=1'@@@",
       "@@@STEP_LOG_LINE@stdout@moar@@@",
-      "@@@STEP_LOG_END@stdout@@@",
-      "@@@STEP_LOG_LINE@diff@+ cool_flag: a=1@@@",
-      "@@@STEP_LOG_LINE@diff@- clang: 0@@@",
-      "@@@STEP_LOG_LINE@diff@- coverage: 1@@@",
-      "@@@STEP_LOG_LINE@diff@- gomadir: '[CACHE]/cipd/goma'@@@",
-      "@@@STEP_LOG_LINE@diff@  target_arch: x64@@@",
-      "@@@STEP_LOG_LINE@diff@- use_goma: 1@@@",
-      "@@@STEP_LOG_END@diff@@@",
-      "@@@STEP_WARNINGS@@@"
+      "@@@STEP_LOG_END@stdout@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::v8]/resources/patch_mb_config.py",
       "[SLAVE_BUILD]/v8/infra/mb/mb_config.pyl",
       "/path/to/tmp/"
     ],
@@ skipping 183 matching lines @@
     "~followup_annotations": [
       "@@@STEP_LINK@report@https://storage.googleapis.com/chromium-v8/linux64_gcov_rel/f2cbea7e89a45f46819777bb78a1f5bd0241f64c/index.html@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]