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

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https://hg.mozilla.org/integration/gaia-central/rev/5252a238167b
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #16736 from crdlc/bug-977094

Bug 977094 - [Download Manager] No error is displayed if you try deletin...

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https://hg.mozilla.org/integration/gaia-central/rev/0d01d483a746
Author: crdlc <crdlc@tid.es>
Desc: Bug 977094 - [Download Manager] No error is displayed if you try deleting a downloaded file while the device is connected as USB
Bumping manifests a=b2g-bump