Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/a7531712e830
Author: Zac <zcampbell@mozilla.com>
Desc: Revert "Bug 1086563 - Write test to verify offline behaviour of the RocketBar"

This reverts commit 94bc14f611fbe55bdef2f00c20be899b8ea0b918.

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https://hg.mozilla.org/integration/gaia-central/rev/f4263a2ae9e3
Author: viorelaioia <viorela.ioia@softvision.ro>
Desc: Merge pull request #25661 from zacc/bug_1084306

Bug 1084306 - gaia-ui-tests Remove support for external resources over c...

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https://hg.mozilla.org/integration/gaia-central/rev/b1384fca24bb
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 1084306 - gaia-ui-tests Remove support for external resources over cellular data
Bumping manifests a=b2g-bump