Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_4/rev/4887bea5dae8
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Merge pull request #20892 from dominickuo/bug-998956-3

Bug 998956 - [MediaDB] Ignore the time difference when it is multiple of 10 minutes and less than 12 hours, r=davidflanagan
Bumping manifests a=b2g-bump