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

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https://hg.mozilla.org/integration/gaia-2_0/rev/b7b6d803748b
Author: Greg Weng <snowmantw@gmail.com>
Desc: Merge pull request #21796 from snowmantw/issue1023500-v2.0

Bug 1023500 - [VsD Refresh] Lockscreen Visual Refresh > Notifications no...

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https://hg.mozilla.org/integration/gaia-2_0/rev/ecd6c5392207
Author: Greg Weng <snowmantw@gmail.com>
Desc: Bug 1023500 - [VsD Refresh] Lockscreen Visual Refresh > Notifications not to spec
Bumping manifests a=b2g-bump