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

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https://hg.mozilla.org/integration/gaia-central/rev/789b4d21f14c
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #21994 from viorelaioia/bug-1041543

Bug 1041543 - Disable tests affected by Bug 1041510

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https://hg.mozilla.org/integration/gaia-central/rev/4608179bbe4f
Author: Viorela Ioia <viorelaioia@gmail.com>
Desc: Bug 1041543 - Disable tests affected by Bug 1041510
Bumping manifests a=b2g-bump