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

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https://hg.mozilla.org/integration/gaia-central/rev/43778f93795d
Author: vingtetun <21@vingtetun.org>
Desc: Merge pull request #19654 from theres-waldo/bug998025

Bug 998025 - Put overscrolling behind a developer pref. r=vingtetun

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https://hg.mozilla.org/integration/gaia-central/rev/8ad64ccf63ed
Author: Botond Ballo <botond@mozilla.com>
Desc: Bug 998025 - Put overscrolling behind a developer pref. r=vingtetun
Bumping manifests a=b2g-bump