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

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https://hg.mozilla.org/integration/gaia-central/rev/5f8941059abc
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #25420 from gaye/bug-821604

Bug 821604 - Don't start periodic sync until we have a calendar that needs a real sync operation r=millermedeiros

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https://hg.mozilla.org/integration/gaia-central/rev/2dac010bee4f
Author: gaye <gaye@mozilla.com>
Desc: Bug 821604 - Don't start periodic sync until we have a calendar that needs a real sync operation
Bumping manifests a=b2g-bump