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

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https://hg.mozilla.org/integration/gaia-central/rev/e596a7138422
Author: ochameau <poirot.alex@gmail.com>
Desc: Merge pull request #12299 from ochameau/build-exceptions

Bug 917793 - Ensure printing exceptions in js build scripts r=yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/6465882eb932
Author: Alexandre Poirot <poirot.alex@gmail.com>
Desc: Bug 917793 - Ensure printing exceptions in js build scripts r=yurenju