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

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https://hg.mozilla.org/integration/gaia-central/rev/0e6e6c54c681
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #15547 from MBRSL/bug-961970-layout

Bug 961970 - [UITest] change layout with Building Blocks, r=gasolin

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https://hg.mozilla.org/integration/gaia-central/rev/5273f26779b1
Author: Tom Jao <tjao@mozilla.com>
Desc: Bug 961970 - [UITest] change layout with Building Blocks
Bumping manifests a=b2g-bump