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

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https://hg.mozilla.org/integration/gaia-central/rev/af269f2f1db3
Author: Ryan VanderMeulen <ryanvm@gmail.com>
Desc: Merge pull request #24654 from oklang/Update-links-to-fetch-shared-style-from-default-theme

Bug 1069840 - Update apps links to fetch shared style from default theme.

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https://hg.mozilla.org/integration/gaia-central/rev/51aef450f51d
Author: Olle Klang <olle.klang@sonymobile.com>
Desc: Update links to fetch gaia-theme from default theme.
Bumping manifests a=b2g-bump