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

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https://hg.mozilla.org/integration/gaia-central/rev/419104f37481
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #15872 from gabrielesvelto/bug-960507

Bug 960507 - Properly remove the onheld event handler when doing a second call r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/8c123d4dd78b
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Bug 960507 - Properly remove the onheld event handler when doing a second call r=etienne
Bumping manifests a=b2g-bump