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

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https://hg.mozilla.org/integration/gaia-central/rev/d7bb79d50e95
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #13824 from huchengtw-moz/video/Bug_938967_00-00_is_not_handle_correctly

Bug 938967 - [fugu][hamachi]The video had be sought to 00:00 could not b..., r=djf

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https://hg.mozilla.org/integration/gaia-central/rev/4e2c8af710a6
Author: John Hu <johu@mozilla.com>
Desc: Bug 938967 - [fugu][hamachi]The video had be sought to 00:00 could not be played from background to foreground