Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-2_0/rev/83fe974318c2
Author: mai <mri@tid.es>
Desc: Bug 1088575 - [LockScreen][EmergencyCall]After click 'More info' in app permission, enter emergency call will get all functionalities broken

Conflicts:
	apps/system/test/unit/lockscreen_test.js
Bumping manifests a=b2g-bump