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

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https://hg.mozilla.org/integration/gaia-central/rev/77a90d19d2c6
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #14966 from kumarrishav/issue-944289

Bug 944289 [UITEST] add Compose Email activity, r=gasolin

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https://hg.mozilla.org/integration/gaia-central/rev/2bd75dd1c8be
Author: kumarrishav <reactiverishav007@gmail.com>
Desc: Bug 944289 [UITEST] add Compose Email activity - bug fixed