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

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https://hg.mozilla.org/integration/gaia-central/rev/ab3e83ebb38a
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #18264 from gaye/revert-28933e686babd4d95b37e6056e4febc0480ff759

Revert "Merge pull request #18255 from evanxd/bug-988516"

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https://hg.mozilla.org/integration/gaia-central/rev/a9de83e21f47
Author: gaye <gaye@mozilla.com>
Desc: Revert "Merge pull request #18255 from evanxd/bug-988516"

This reverts commit 28933e686babd4d95b37e6056e4febc0480ff759, reversing
changes made to 68d8e6897f326a8980c81da80bf8a76440ef3faf.
Bumping manifests a=b2g-bump