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

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https://hg.mozilla.org/integration/gaia-central/rev/6e20235b0613
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #23010 from KevinGrandon/bug_1048458_rocketbar_dialer_weirdness

Bug 1048458 - [B2G][2.1][Dialer] Calling a second number while another call is in progress cover's touchpad in Dialer app

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https://hg.mozilla.org/integration/gaia-central/rev/25735263fe21
Author: Vivien Nicolas <vnicolas@mozilla.com>
Desc: Bug 1048458 - [B2G][2.1][Dialer] Calling a second number while another call is in progress cover's touchpad in Dialer app r=kgrandon
Bumping manifests a=b2g-bump