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

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https://hg.mozilla.org/integration/gaia-central/rev/a54cc0c1ff0d
Author: James Lal <james@lightsofapollo.com>
Desc: Merge pull request #12255 from lightsofapollo/travis-parallel

Bug 917044 - Run gjslint, unit tests and integration tests in parallel

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https://hg.mozilla.org/integration/gaia-central/rev/2f6b3ef3d6ee
Author: James Lal <james@lightsofapollo.com>
Desc: Bug 917044 - Run gjslint, unit tests and integration tests in parallel