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

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https://hg.mozilla.org/integration/gaia-central/rev/2977ae6150d7
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #15000 from cctuan/956208

Bug 956208 - [Gaia][Build] add gaiaDir variable in getPid function

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https://hg.mozilla.org/integration/gaia-central/rev/59faa7c52b52
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 956208 - [Gaia][Build] add gaiaDir variable in getPid function