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

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https://hg.mozilla.org/integration/gaia-central/rev/6a6db1dac429
Author: Carsten Book <tomcat@mozilla.com>
Desc: Merge pull request #21414 from mdotoum/clock-issue-964036

Bug 964036 - (gaia-rtl) Support RTL for Clock App r=nefzaoui

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https://hg.mozilla.org/integration/gaia-central/rev/580239bc1c99
Author: MD Otoum <md.otoum@gmail.com>
Desc: Bug 964036 - (gaia-rtl) Support RTL for Clock App r=nefzaoui
Bumping manifests a=b2g-bump