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

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https://hg.mozilla.org/integration/gaia-central/rev/8dd8d8a8d987
Author: Trif Andrei-Alin <trifandreialin@gmail.com>
Desc: Merge pull request #14825 from bobsilverberg/ftu_frames

Bug 937336 - Remove where possible explicit frame switching

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https://hg.mozilla.org/integration/gaia-central/rev/976214918eb6
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Bug 937336 - Remove where possible explicit frame switching

Replace calls to marionette.switch_to_frame(self.app.frame) in FTU test with apps.switch_to_displayed_app()

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https://hg.mozilla.org/integration/gaia-central/rev/e127a5af0224
Author: Trif Andrei-Alin <trifandreialin@gmail.com>
Desc: Merge pull request #14820 from bobsilverberg/contacts_frames

Bug 937336 - Remove where possible explicit frame switching

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https://hg.mozilla.org/integration/gaia-central/rev/1ed9189786ae
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Bug 937336 - Remove where possible explicit frame switching

Changes to Contacts app, where possible