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

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https://hg.mozilla.org/integration/gaia-central/rev/dc7f1464c351
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #14899 from gasolin/issue-952466

Bug 952466 - [Window Management] Improve app window and dialogs jsdoc, r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/1b88370b0c36
Author: gasolin <gasolin@gmail.com>
Desc: Bug 952466 - [Window Management] Improve app window and dialogs jsdoc