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

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https://hg.mozilla.org/integration/gaia-central/rev/e21d1a1554ae
Author: Arnau <arnau@arnaumarch.com>
Desc: Merge pull request #21915 from pacorampas/1035612

Bug 1035612 - [Dialer] 'Hang up' and 'answer' buttons enlarge a little bit when tapping on 'answer' button for 2nd call, when 1st one is active r=rik

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https://hg.mozilla.org/integration/gaia-central/rev/807c751e6568
Author: Paco Rampas <pacorampas@gmail.com>
Desc: Bug 1035612 - [Dialer] 'Hang up' and 'answer' buttons enlarge a little bit when tapping on 'answer' button for 2nd call, when 1st one is active
Bumping manifests a=b2g-bump