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

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https://hg.mozilla.org/integration/gaia-central/rev/6976dbea77ec
Author: viorelaioia <viorela.ioia@softvision.ro>
Desc: Merge pull request #25488 from chirarobert/fix_dialer_test

Bug 1088585 - [v2.2] Fix test_dialer_make_call jenkins failure

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https://hg.mozilla.org/integration/gaia-central/rev/ecbd1ceca38f
Author: Robert Chira <robertchira@P5075.(none)>
Desc: Bug 1088585 - [v2.2] Fix test_dialer_make_call jenkins failure
Bumping manifests a=b2g-bump