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

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https://hg.mozilla.org/integration/gaia-central/rev/ef983063519c
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #16174 from viorelaioia/bug_970936

Bug 970936 - Fix intermittent failure in test_gallery_empty.py

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https://hg.mozilla.org/integration/gaia-central/rev/45abe3a2093c
Author: Viorela Ioia <viorelaioia@gmail.com>
Desc: Bug 970936 - Fix intermittent failure in test_gallery_empty.py
Bumping manifests a=b2g-bump