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

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https://hg.mozilla.org/integration/gaia-central/rev/ed21b3f36335
Author: steveck-chung <schung@mozilla.com>
Desc: Merge pull request #17878 from steveck-chung/FM-2.25X

Bug 983077 - [MADAI][FMRadio] @2.25x assets update for FMRadio. r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/0a5173dcfc3a
Author: Steve Chung <schung@mozilla.com>
Desc: Bug 983077 - [MADAI][FMRadio] @2.25x assets update for FMRadio

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https://hg.mozilla.org/integration/gaia-central/rev/3fc0920f1e50
Author: Florin Strugariu <bebef_1987@yahoo.com>
Desc: Merge pull request #17879 from AndreiH/bug990985

Bug 990985 - [master][v1.4] Let's xfail test_settings_airplane_mode.Test...

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https://hg.mozilla.org/integration/gaia-central/rev/825e88e7b440
Author: Andrei Hutusoru <andreihutusoru@P5069.(none)>
Desc: Bug 990985 - [master][v1.4] Let's xfail test_settings_airplane_mode.TestAirplaneMode
Bumping manifests a=b2g-bump