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

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https://hg.mozilla.org/integration/gaia-central/rev/25fa9da53e3e
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #13530 from etiennesegonzac/bug-933279-conf-call-attention-screen-show

Bug 933279 - Always displaying the call screen attention screen for each extra incoming or outgoing call. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/eb07593a9df2
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 933279 - Updating the telephony part of the ScreenManager to work
with conference calls. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/a781dbc27a0d
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #13799 from etiennesegonzac/bug-939773-asyncstorage-error-suggestion

Bug 939773 - Fixing a ReferenceError: asyncStorage the first time the keypad suggestion is used after a cold launch. r=rik

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https://hg.mozilla.org/integration/gaia-central/rev/0364e7df293e
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 939773 - Fixing a ReferenceError: asyncStorage the first time the
keypad suggestion is used after a cold launch.