message: Remove definition of WEBRTC_MOZILLA_BUILD.
  This macro is not used in WebRTC code.
  Cr-Commit-Position: refs/heads/main@{#35872}
diff: @@ -128,10 +128,6 @@ config("common_inherited_config") {
  defines += [ "WEBRTC_ENABLE_OBJC_SYMBOL_EXPORT" ]
  }
  - if (build_with_mozilla) {
  - defines += [ "WEBRTC_MOZILLA_BUILD" ]
  - }
  -
  if (!rtc_builtin_ssl_root_certificates) {
  defines += [ "WEBRTC_EXCLUDE_BUILT_IN_SSL_ROOT_CERTS" ]
  }
  