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

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https://hg.mozilla.org/integration/gaia-central/rev/b68b646d61d7
Author: Florin Strugariu <florin.strugariu@softvision.ro>
Desc: Merge pull request #26718 from viorelaioia/bug_1102931_1

Bug 1102931 - Intermittent test_ftu_with_tour.py TestFtu.test_ftu_with_t...

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https://hg.mozilla.org/integration/gaia-central/rev/91c999194092
Author: Viorela Ioia <viorelaioia@gmail.com>
Desc: Bug 1102931 - Intermittent test_ftu_with_tour.py TestFtu.test_ftu_with_tour
Bumping manifests a=b2g-bump