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

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https://hg.mozilla.org/integration/gaia-central/rev/1cd16812e365
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #18735 from viorelaioia/bug_968744

Bug 968744 - Update test_receive_active_sync_email to check for incoming...

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https://hg.mozilla.org/integration/gaia-central/rev/3b9c7feea9eb
Author: Viorela Ioia <viorelaioia@gmail.com>
Desc: Bug 968744 - Update test_receive_active_sync_email to check for incoming notification

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https://hg.mozilla.org/integration/gaia-central/rev/753561709b03
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #18239 from jmcanterafonseca/arnau_fix_edit_mode

Bug 990478 - Replace confirm [BB] with edit mode [BB] in [Contacts]

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https://hg.mozilla.org/integration/gaia-central/rev/02381ce472a7
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 990478 - Replace confirm [BB] with edit mode [BB] in [Contacts]
Bumping manifests a=b2g-bump