Bumping gaia.json for 2 gaia-1_3 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_3/rev/210164b90a15
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Merge pull request #15900 from mikehenrty/bug-959800-uplift

Merge pull request #15744 from mikehenrty/bug-959800-mozbrowser, r=auswer

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https://hg.mozilla.org/integration/gaia-1_3/rev/ee0f677a8f26
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Merge pull request #15744 from mikehenrty/bug-959800-mozbrowser

Bug 959800 - [Offline] mozbrowser iframes don't display correct offline ...
(cherry picked from commit f1928155eb29b6b1766ba6ca8380221a4f670d60)

Conflicts:
	apps/system/js/net_error.js
	build/jshint/xfail.list