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

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https://hg.mozilla.org/integration/gaia-central/rev/656ca946983e
Author: RickyChien <RickyChien@users.noreply.github.com>
Desc: Merge pull request #25934 from RickyChien/bug-969215

Bug 969215 - Execute |make| should only build specific apps we modified r=@cctuan, r=@ochameau

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https://hg.mozilla.org/integration/gaia-central/rev/d39f6817c686
Author: Ricky Chien <ricky060709@gmail.com>
Desc: Bug 969215 - Execute |make| should only build specific apps we modified

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https://hg.mozilla.org/integration/gaia-central/rev/ef0c18e8ba4e
Author: albertopq <albert.pastor@gmail.com>
Desc: Merge pull request #25876 from albertopq/1093329-edit-header-downloads

Bug 1093329 - Hiding edit mode by default in Settings - Downloads r=arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/ef3fd12c4fe5
Author: albertopq <apastor@mozilla.com>
Desc: Bug 1093329 - Hiding edit mode by default in Settings - Downloads
Bumping manifests a=b2g-bump