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

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https://hg.mozilla.org/integration/gaia-central/rev/955218ada6da
Author: Amir Nissim <amirnissim@gmail.com>
Desc: Merge pull request #15556 from EverythingMe/bug-948195

Bug 948195 followup - compress new PNG files

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https://hg.mozilla.org/integration/gaia-central/rev/f61adf3043cd
Author: Amir Nissim <amirnissim@gmail.com>
Desc: Bug 948195 followup - compress new PNG files
Bumping manifests a=b2g-bump