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

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https://hg.mozilla.org/integration/gaia-1_3/rev/874fcd42519e
Author: EragonJ <eragonj@eragonj.me>
Desc: Merge pull request #16870 from EragonJ/v1.3-bug-979672

Bug 979672 - On 1.3, marionette_js keeps failing in Travis

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https://hg.mozilla.org/integration/gaia-1_3/rev/a1f38eb95a67
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 979672 - On 1.3, marionette_js keeps failing in Travis
Bumping manifests a=b2g-bump