Bumping gaia.json for 5 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/524def619c90
Author: Hubert Figuière <hub@figuiere.net>
Desc: Merge pull request #14771 from hfiguiere/bug951235

Bug 951235 - Fix improper use of back ticks to output. r=julienw

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https://hg.mozilla.org/integration/gaia-central/rev/ef312a0efdb5
Author: Hubert Figuière <hub@figuiere.net>
Desc: Bug 951235 - Fix improper use of back ticks to output.

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https://hg.mozilla.org/integration/gaia-central/rev/35cbd178b0b0
Author: Hubert Figuière <hub@figuiere.net>
Desc: Merge pull request #15288 from hfiguiere/bug958652

Bug 958652 - pass MOZPERFOUT to redirect mozperf JSON data to a file. Default == stdout. r=julienw

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https://hg.mozilla.org/integration/gaia-central/rev/d2d55b4f7676
Author: Hubert Figuière <hub@figuiere.net>
Desc: Bug 958652 - nit: missing #

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https://hg.mozilla.org/integration/gaia-central/rev/54a45f8fa8e7
Author: Hubert Figuière <hub@figuiere.net>
Desc: Bug 958652 - pass MOZPERFOUT to redirect mozperf JSON data to a file. Default == stdout.