Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/556fb9489256
Author: punamdahiya <punamdahiya@yahoo.com>
Desc: Merge pull request #20971 from punamdahiya/Bug1028800

Bug1028800-[Gallery]- Fix of gallery pick activity is dismissed when invoking app goes to background r=djf

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https://hg.mozilla.org/integration/gaia-central/rev/3766e81e072b
Author: Punam Dahiya <punamdahiya@yahoo.com>
Desc: Bug1028800-[Gallery]- Fix of gallery pick activity is dismissed when invoking app goes to background r=djf
Bumping manifests a=b2g-bump