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

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https://hg.mozilla.org/integration/gaia-central/rev/5a39a3762c60
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #12471 from yurenju/terminate-build

Bug 919377 - terminate build process if get error from xpcshell script r=@ochameau

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https://hg.mozilla.org/integration/gaia-central/rev/b9e0c355689c
Author: Yuren Ju <yurenju@gmail.com>
Desc: Bug 919377 - terminate build process if get error from xpcshell script