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

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https://hg.mozilla.org/integration/gaia-central/rev/770708ef8803
Author: gitmai <mri@tid.es>
Desc: Merge pull request #15148 from gitmai/bug-949977-Topup-option-not-visible

Bug 949977 - [Costcontrol] Topup option not visible after FTE finished
r=salva

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https://hg.mozilla.org/integration/gaia-central/rev/6c4608ff5482
Author: mai <mri@tid.es>
Desc: Bug 949977 - [Costcontrol] Topup option not visible after FTE finished