Revert of Enforce marking "override" for functions overriding Blink. (patchset #19 id:360001 of https://codereview.chromium.org/1370923002/ )

Reason for revert:
Missed one.

Original issue's description:
> Enforce marking "override" for functions overriding Blink.
>
> BUG=535367
> TEST=it all stays working
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
> TBR=ben@chromium.org
>
> Committed: https://crrev.com/32ff552858e014d454ce8b181f5aca1dfcf8f8fd
> Cr-Commit-Position: refs/heads/master@{#363482}

TBR=thakis@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=535367

Review URL: https://codereview.chromium.org/1504913002

Cr-Original-Commit-Position: refs/heads/master@{#363492}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 50e3df675d58385e566645effb6ccfd3c8562443

common.gypi

@@ -2227,8 +2227,7 @@
               'clang_dynlib_flags%': '',
             }],
           ],
-          'clang_plugin_args%': '-Xclang -plugin-arg-find-bad-constructs -Xclang check-templates '
+          'clang_plugin_args%': '-Xclang -plugin-arg-find-bad-constructs -Xclang check-templates ',
-          '-Xclang -plugin-arg-find-bad-constructs -Xclang enforce-overriding-blink ',
         },
         # If you change these, also change build/config/clang/BUILD.gn.
         'clang_chrome_plugins_flags%':

config/clang/BUILD.gn

@@ -40,10 +40,6 @@ config("find_bad_constructs") {
       "-plugin-arg-find-bad-constructs",
       "-Xclang",
       "check-templates",
-      "-Xclang",
-      "-plugin-arg-find-bad-constructs",
-      "-Xclang",
-      "enforce-overriding-blink",
     ]
   }
 }