Exclude frontend_server from the license crawl (#4645)

tools/licenses/lib/main.dart

@@ -2106,6 +2106,7 @@ class RepositoryFlutterDirectory extends RepositoryDirectory {
         && entry.name != 'examples'
         && entry.name != 'build'
         && entry.name != 'travis'
+        && entry.name != 'frontend_server'
         && super.shouldRecurse(entry);
   }
 

travis/licenses_golden/licenses_flutter

@@ -1549,8 +1549,6 @@ ORIGIN: ../../../LICENSE
 TYPE: LicenseType.bsd
 FILE: ../../../flutter/DEPS
 FILE: ../../../flutter/content_handler/meta/sandbox
-FILE: ../../../flutter/frontend_server/bin/starter.dart
-FILE: ../../../flutter/frontend_server/lib/server.dart
 FILE: ../../../flutter/lib/io/dart_io.cc
 FILE: ../../../flutter/lib/io/dart_io.h
 FILE: ../../../flutter/lib/snapshot/libraries.json