remove docgen remnants from repo, update CHANGELOG

tools/apps/update_homebrew/bin/update_homebrew.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library update_homebrew;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 151 matching lines @@
 
   resource 'dartium' do
     version '$stableVersion'
     url '$urlBase/stable/release/${revisions['stable']}/$dartiumFile'
     sha256 '${hashes['stable'][dartiumFile]}'
   end
 
   def install
     libexec.install Dir['*']
     bin.install_symlink "#{libexec}/bin/dart"
-    bin.write_exec_script Dir["#{libexec}/bin/{pub,docgen,dart?*}"]
+    bin.write_exec_script Dir["#{libexec}/bin/{pub,dart?*}"]
 
     if build.with? 'dartium'
       dartium_binary = 'Chromium.app/Contents/MacOS/Chromium'
       prefix.install resource('dartium')
       (bin+"dartium").write shim_script dartium_binary
     end
 
     if build.with? 'content-shell'
       content_shell_binary = 'Content Shell.app/Contents/MacOS/Content Shell'
       prefix.install resource('content_shell')
@@ skipping 77 matching lines @@
 
       await runGit(['push']);
     } finally {
       await tempDir.delete(recursive: true);
     }
   }, onError: (error, chain) {
     print(error);
     print(chain.terse);
   });
 }