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

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https://hg.mozilla.org/integration/gaia-central/rev/5256ce74a178
Author: James Lal <james@lightsofapollo.com>
Desc: Merge pull request #24728 from lightsofapollo/bug-1077162

Bug 1077162 - Set git email/name so we can merge when needed in tc r=kgr...

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https://hg.mozilla.org/integration/gaia-central/rev/018dc6e9ed11
Author: James Lal <james@lightsofapollo.com>
Desc: Bug 1077162 - Set git email/name so we can merge when needed in tc r=kgrandon
Bumping manifests a=b2g-bump