Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/e63ca851cb32
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #21944 from wlach/1039739-2

Bug 1039739 - Make it more clear what command we're executing;r=yuren

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https://hg.mozilla.org/integration/gaia-central/rev/d8802cfd38a5
Author: William Lachance <wlachance@mozilla.com>
Desc: Bug 1039739 - Make it more clear what command we're executing;r=yuren

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https://hg.mozilla.org/integration/gaia-central/rev/0f061f41a849
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #21841 from tenmilestereo/master

Bug 1031998 - JSHint now throwing no errors r=@yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/a146f315d66b
Author: Lewis Cowper <lewis@lewiscowper.org>
Desc: Bug 1031998 - Fix jshint error for build/config/payment-dev-prefs.js
Bumping manifests a=b2g-bump