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

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https://hg.mozilla.org/integration/gaia-central/rev/7860ffa61a53
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #19911 from jmcanterafonseca/fix_merge_photos

Bug 1002787 - [B2G][Contacts]when merging two contacts that both have pi...

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https://hg.mozilla.org/integration/gaia-central/rev/61f0aa852791
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 1002787 - [B2G][Contacts]when merging two contacts that both have pictures, the picture of the contact that initiated the merge is not preserved.

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https://hg.mozilla.org/integration/gaia-central/rev/67ad404fa340
Author: Min-Zhong "John" Lu <mnjul@users.noreply.github.com>
Desc: Merge pull request #19712 from mnjul/bug_950884_lockscreen_visual_refresh

Bug 950884 - [VsD Refresh] Lockscreen Visual Refresh. r=gweng

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https://hg.mozilla.org/integration/gaia-central/rev/3d74dd45e34a
Author: John Lu [:mnjul] <jlu@mozilla.com>
Desc: Bug 950884 - [VsD Refresh] Lockscreen Visual Refresh
Bumping manifests a=b2g-bump