Bumping gaia.json for 6 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/b638f8093c24
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Merge pull request #18421 from Rik/always-contact-home-994575

Bug 994575 - Add a call should always display the list of contacts r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/e1c4306ce43b
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Bug 994575 - Add a call should always display the list of contacts

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https://hg.mozilla.org/integration/gaia-central/rev/091a8852196a
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: JSHint cleaning, will be squashed

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https://hg.mozilla.org/integration/gaia-central/rev/a52ecceea008
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 996252 - Disable failing Settings test on MacOS TBPL a=testonly r=me

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https://hg.mozilla.org/integration/gaia-central/rev/6df88805261f
Author: Amir Nissim <amirnissim@gmail.com>
Desc: Merge pull request #18515 from EverythingMe/bug-995949

Bug 995949 - Cannot add smart collection to homescreen [r=ranbena]

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https://hg.mozilla.org/integration/gaia-central/rev/be8e2c0a99e2
Author: Amir Nissim <amirnissim@gmail.com>
Desc: Bug 995949 - Cannot add smart collection to homescreen [r=ranbena]
Bumping manifests a=b2g-bump