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

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https://hg.mozilla.org/integration/gaia-central/rev/6eebea42f3f6
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Merge pull request #13123 from pivanov/bug-931555

Bug 931555 - [Bluetooth] - wrong button style on file transfer failed screen

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https://hg.mozilla.org/integration/gaia-central/rev/55ca2e71c1af
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 931555 - [Bluetooth] - wrong button style on file transfer failed screen