Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/780902e6d615
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #20245 from eeejay/bug-970658

Bug 970658 - Cache downloaded extensions in build_stage. r=ochameau

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https://hg.mozilla.org/integration/gaia-central/rev/c5329cb90efb
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: fix build integration tests

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https://hg.mozilla.org/integration/gaia-central/rev/89cbd0c9a999
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: change to http from https

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https://hg.mozilla.org/integration/gaia-central/rev/67b7ac58951e
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 970658 - Cache downloaded extensions in build_stage
Bumping manifests a=b2g-bump