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

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https://hg.mozilla.org/integration/gaia-central/rev/fff83f755600
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Merge pull request #10690 from Rik/restrict-linter-hook-887873

Bug 887873 - precommit hook should check only apps/ and shared/ r=julienw

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https://hg.mozilla.org/integration/gaia-central/rev/95946920b1e4
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Bug 887873 - precommit hook should check only apps/ and shared/