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/b6ab9ddc2457
Author: steveck-chung <schung@mozilla.com>
Desc: Merge pull request #15526 from steveck-chung/bug-961231

Bug 961231 - [B2G][SMS]To: Text field’s subtext region is truncated. r=julienw(cherry picked from commit 8153f963205701dba9fceb52982a0aba67544bad)