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

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https://hg.mozilla.org/integration/gaia-central/rev/d750c1984a30
Author: Michał Budzyński <michal@virtualdesign.pl>
Desc: Merge pull request #19343 from michalbe/Bug935636

Bug 935636 - Avoid duplicating data on contact merge

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https://hg.mozilla.org/integration/gaia-central/rev/ab051702872f
Author: Michal Budzynski <michal@virtualdesign.pl>
Desc: Bug 935636 - Avoid duplicating data on contact merge
Bumping manifests a=b2g-bump