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

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https://hg.mozilla.org/integration/gaia-central/rev/fb78b6585e31
Author: Miller Medeiros <miller@millermedeiros.com>
Desc: Merge pull request #20153 from millermedeiros/event-detail-963394

Bug 963394 - Visual refresh for event detail page r=gaye

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https://hg.mozilla.org/integration/gaia-central/rev/6b1c35454e93
Author: Evan Xd <itoyxd@gmail.com>
Desc: Bug 963394 - Visual refresh for event detail page
Bumping manifests a=b2g-bump