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

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https://hg.mozilla.org/integration/gaia-central/rev/7064f54c5631
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #20703 from KevinGrandon/bug_1020158_collections_iac_retry

Retry: Bug 1020158 - Send IAC message to start the population process

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https://hg.mozilla.org/integration/gaia-central/rev/ffd672941b06
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1027708 - Disable test_cleanup_gaia for mac r=me

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https://hg.mozilla.org/integration/gaia-central/rev/b5d950b2db23
Author: Carmen Jimenez Cabezas <cjc@tid.es>
Desc: Bug 1020158 - Send IAC message to start the population process
Bumping manifests a=b2g-bump