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

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https://hg.mozilla.org/integration/gaia-1_3/rev/dc594bdeed5c
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #17556 from shamenchens/Bug979086-Gallery-Landscape

Bug 979086 SMS Gallery Landscape Mode

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https://hg.mozilla.org/integration/gaia-1_3/rev/cb9ba8ce3108
Author: Sherman Chen <shamen.chens@gmail.com>
Desc: Bug 979086 SMS Gallery Landscape Mode, Dup:Bug960215
Apply this patch: https://github.com/mozilla-b2g/gaia/pull/15512
Bumping manifests a=b2g-bump