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

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https://hg.mozilla.org/integration/gaia-central/rev/849c30a80401
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #22257 from staktrace/pref-gaia

Bug 1042152 - Expose gaia developer settings to toggle low-precision/pro...

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https://hg.mozilla.org/integration/gaia-central/rev/2fa53f810bb6
Author: Kartikaya Gupta <kgupta@mozilla.com>
Desc: Bug 1042152 - Expose gaia developer settings to toggle low-precision/progressive painting and low-opacity behavior. r=vingtetun
Bumping manifests a=b2g-bump