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

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https://hg.mozilla.org/integration/gaia-central/rev/618c84f83b45
Author: Douglas Sherk <github@sherk.me>
Desc: Merge pull request #19253 from DouglasSherk/971446-keyboard-bubbles-re

Bug 971446 - [Keyboard] Add a slight delay to text bubbles and highlighting disappearing. r=rudyl

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https://hg.mozilla.org/integration/gaia-central/rev/c424dcd50c5d
Author: DouglasSherk <github@sherk.me>
Desc: Bug 971446 - [Keyboard] Add a slight delay to text bubbles and highlighting disappearing. r=rudyl
Bumping manifests a=b2g-bump