fix comment typo in BUILD.gn

BUG=none
R=andrew@webrtc.org

Review URL: https://codereview.webrtc.org/1370143004 .

Patch from Andrew Bonventre <andybons@chromium.org>.
1 file changed
tree: 60b7b463e727c0f34daaafd9ba572a190a3fc5bb
  1. dl/
  2. codereview.settings
  3. LICENSE
  4. OWNERS
  5. README.chromium