Bumping gaia.json for 1 gaia-1_3 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_3/rev/855535035eb1
Author: steveck-chung <schung@mozilla.com>
Desc: Merge pull request #14539 from steveck-chung/message-timestamp-changes

Bug 944881 - Gaia should interpret timestamps as long-long numbers. r=julienw, a=blocking-b2g 1.3+
(cherry picked from commit 87345e3947da71386552561d5f15109955d4fe15)