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

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https://hg.mozilla.org/integration/gaia-central/rev/74ed51578aa6
Author: Florin Strugariu <bebef_1987@yahoo.com>
Desc: Merge pull request #14078 from zacc/bug_942107_camera

Bug 942107 - Camera app. Be smart and reduce locators.

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https://hg.mozilla.org/integration/gaia-central/rev/f39520348031
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 942107 - Camera app. Be smart and reduce locators.

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https://hg.mozilla.org/integration/gaia-central/rev/5bbbedf7a67a
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Merge pull request #14062 from zacc/bug_939062_pt2

Bug 939062 - Part 2 address intermittent failure in test_add_contact_to_...

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https://hg.mozilla.org/integration/gaia-central/rev/c59fd8caa6ee
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 939062 - Part 2 address intermittent failure in test_add_contact_to_favorites.py