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

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https://hg.mozilla.org/integration/gaia-central/rev/8acca712933d
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Merge pull request #15955 from Rik/inactive-group-after-finishing-call-966951

Bug 966951 - "Group Call" is inactive when received call is hung up r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/57c4fd44c1dc
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Bug 966951 - "Group Call" is inactive when received call is hung up
Bumping manifests a=b2g-bump