Remove a workaround for Protobuf v25.0 from protobuf.gyp

This is a follow up commit to my previous commit [1] for #841, which
made protobuf.gyp compatible with Protobuf v25.0 to work around a
compile error [2].

Now that Mozc has switched to Protobuf v26.0 [3] (#871), this work
around is no longer necessary.

 [1]: 013e8aa
 [2]: protocolbuffers/protobuf#14602
 [3]: 0df12d0

#codehealth

PiperOrigin-RevId: 616344978

src/protobuf/protobuf.gyp

@@ -123,13 +123,6 @@
           'msvs_disabled_warnings': [
             '<@(msvc_disabled_warnings_for_protoc)',
           ],
-          'msvs_settings': {
-            'VCCLCompilerTool': {
-              'AdditionalOptions': [
-                '/permissive',  # https://github.com/protocolbuffers/protobuf/issues/14602
-              ],
-            },
-          },
           'xcode_settings': {
             'USE_HEADERMAP': 'NO',
           },