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

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https://hg.mozilla.org/integration/gaia-central/rev/d97823ac7b01
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #20875 from KevinGrandon/bug_1028681_collections_pinning_entry_points

Bug 1028681 - [Collection app] Contacts and Phone apps cannot be added to Smart Collections

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https://hg.mozilla.org/integration/gaia-central/rev/2d6f4b914268
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1028681 - [Collection app] Contacts and Phone apps cannot be added to Smart Collections r=ranbena

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https://hg.mozilla.org/integration/gaia-central/rev/a5e918e0228e
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #20844 from guilherme-pg/bug1000173-tracking-notification

Bug 1000173 - Display User Icon in Settings When FMD is Remotely Trackin...

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https://hg.mozilla.org/integration/gaia-central/rev/3a66c11eb47b
Author: yglazko <yglazko@yglazko.local>
Desc: Bug 1000173 - Display User Icon in Settings When FMD is Remotely Tracking Device
Bumping manifests a=b2g-bump