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

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https://hg.mozilla.org/integration/gaia-1_3/rev/73b775a71396
Author: AndreiH <andrei.hutusoru@softvision.ro>
Desc: Merge pull request #18224 from viorelaioia/bug_991679

Bug 991679 - [v1.3] Investigate and try to fix test_ftu_skip_tour.TestFt...

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https://hg.mozilla.org/integration/gaia-1_3/rev/7837ae72307d
Author: Viorela Ioia <viorelaioia@gmail.com>
Desc: Bug 991679 - [v1.3] Investigate and try to fix test_ftu_skip_tour.TestFtu fails on v1.3
Bumping manifests a=b2g-bump