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

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https://hg.mozilla.org/integration/gaia-central/rev/9b67bad6fa29
Author: Florin Strugariu <bebef_1987@yahoo.com>
Desc: Merge pull request #18747 from zacc/bug_1002465

Bug 1002465 - test_browser_play_you_tube.py - wait for the elements to b...

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https://hg.mozilla.org/integration/gaia-central/rev/17d568aee703
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 1002465 - test_browser_play_you_tube.py - wait for the elements to be displayed rather than present

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https://hg.mozilla.org/integration/gaia-central/rev/ae592f432406
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #18720 from KevinGrandon/bug_1002247_system2_app_authentication_dialog

Bug 1002247 - [System2] AppAuthenticationDialog fixes r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/a0409f14c138
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1002247 - [System2] AppAuthenticationDialog fixes r=alive
Bumping manifests a=b2g-bump