Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/c12dbd6d8315
Author: Martijn <martijn.martijn@gmail.com>
Desc: Merge pull request #26338 from mwargers/audio_channel2

Bug 1094144 - Add a test that ensures test_play_*_video has the correct ...

========

https://hg.mozilla.org/integration/gaia-central/rev/9dc672f9a97b
Author: Martijn Wargers <mwargers@mozilla.com>
Desc: Bug 1094144 - Add a test that ensures test_play_*_video has the correct audio channel opened
Bumping manifests a=b2g-bump