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

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https://hg.mozilla.org/integration/gaia-central/rev/f7e84403d440
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #13061 from bebef1987/marionette_0.6.1

Bug 929999 - Bump marionette_client dependency to 0.6.1 or above

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https://hg.mozilla.org/integration/gaia-central/rev/1d4d2fa99490
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 929999 - Bump marionette_client dependency to 0.6.1 or above