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

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https://hg.mozilla.org/integration/gaia-central/rev/68765d6b3a93
Author: Florin Strugariu <bebef_1987@yahoo.com>
Desc: Merge pull request #21522 from AndreiH/bug_1022693_fix

Bug 1022693 - [UI Tests] Intermittent Travis failure: TEST-UNEXPECTED-FA...

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https://hg.mozilla.org/integration/gaia-central/rev/bd509ae9dd62
Author: Andrei Hutusoru <andreihutusoru@P5069.(none)>
Desc: Bug 1022693 - [UI Tests] Intermittent Travis failure: TEST-UNEXPECTED-FAIL | test_persona_app.py test_persona_app

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https://hg.mozilla.org/integration/gaia-central/rev/4011c56f83af
Author: Florin Strugariu <bebef_1987@yahoo.com>
Desc: Merge pull request #21526 from viorelaioia/bug_931015

Bug 931015 - Re-enable wait_for_notification_toaster_displayed/not_displ...

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https://hg.mozilla.org/integration/gaia-central/rev/3a6ea5fd6ed0
Author: Viorela Ioia <viorelaioia@gmail.com>
Desc: Bug 931015 - Re-enable wait_for_notification_toaster_displayed/not_displayed in system/app.py
Bumping manifests a=b2g-bump