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

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https://hg.mozilla.org/integration/gaia-central/rev/623b1441cb54
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #21710 from pivanov/bug-1035727

Bug 1035727 - [SMS] - remove unused images r=julien

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https://hg.mozilla.org/integration/gaia-central/rev/97f6f19b8b3b
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 1035727 - [SMS] - remove unused images
Bumping manifests a=b2g-bump