Remove --isolated from mb.py

This option is not supported now.

Bug: chromium:1271841
Change-Id: I27dd1531589ac497ef345fff41897a087ace4362
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/239461
Reviewed-by: Takuto Ikuta <tikuta@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Auto-Submit: Junji Watanabe <jwata@google.com>
Cr-Commit-Position: refs/heads/main@{#35449}

tools_webrtc/mb/mb.py

@@ -796,8 +796,6 @@ class MetaBuildWrapper(object):
         self.WriteJSON(
             {
                 'args': [
-                    '--isolated',
-                    self.ToSrcRelPath('%s/%s.isolated' % (build_dir, target)),
                     '--isolate',
                     self.ToSrcRelPath('%s/%s.isolate' % (build_dir, target)),
                 ],