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

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https://hg.mozilla.org/integration/gaia-central/rev/3ff9cbe0526a
Author: Ryan VanderMeulen <ryanvm@gmail.com>
Desc: Merge pull request #24661 from mancas/bug1039501

Bug 1039501 - [User Story] [FOTA] WiFi prioritized for downloading. r=et...

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https://hg.mozilla.org/integration/gaia-central/rev/99c89e33b134
Author: Manuel Casas Barrado <manuel.casasbarrado@telefonica.com>
Desc: Bug 1039501 - [User Story] [FOTA] WiFi prioritized for downloading. r=etienne
Bumping manifests a=b2g-bump