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

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https://hg.mozilla.org/integration/gaia-central/rev/bec42064814a
Author: James Lal <james@lightsofapollo.com>
Desc: Merge pull request #13194 from lightsofapollo/travis-retry

Travis retry

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https://hg.mozilla.org/integration/gaia-central/rev/6ab8c307ac44
Author: James Lal <james@lightsofapollo.com>
Desc: Bug 932489 - Travis retry r=me a=test-only +shepherd