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

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https://hg.mozilla.org/integration/gaia-central/rev/28c1686f93eb
Author: Yoshi Huang <allstars.chh@mozilla.com>
Desc: Merge pull request #18844 from svic/Bug_1002304

Bug 1002304 - Restore state of BT for incoming file transfers. r=evelyn

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https://hg.mozilla.org/integration/gaia-central/rev/6711541b21b3
Author: Arno Puder <arno@puder.org>
Desc: Bug 1002304 - Restore state of BT for incoming file transfers. r=ehung
Bumping manifests a=b2g-bump