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

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https://hg.mozilla.org/integration/gaia-central/rev/3280f72ecdd6
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #20606 from zacc/bug_1019902

Bug 1019902 - Merge and Update test_everythingme_add_collection.py and t...

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https://hg.mozilla.org/integration/gaia-central/rev/47943ae51a2c
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 1019902 - Merge and Update test_everythingme_add_collection.py and test_eme_app_install.py
Bumping manifests a=b2g-bump