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

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https://hg.mozilla.org/integration/gaia-central/rev/463fd6e56dc9
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Merge pull request #15323 from pivanov/bug-949758

Bug 949758 - [B2G][Settings] The highlighter for the language selection box is offset.

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https://hg.mozilla.org/integration/gaia-central/rev/16ebe7853d97
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 949758 - [B2G][Settings] The highlighter for the language selection box is offset.
Bumping manifests a=b2g-bump