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

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https://hg.mozilla.org/integration/gaia-central/rev/da5baf96ef8b
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #15207 from etiennesegonzac/bug-958584-fullscreen-statusbar

Bug 958584 - Swiping from the top to make the status bar appear in fullscreen r=vingtetun

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https://hg.mozilla.org/integration/gaia-central/rev/20c3467bcfac
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 958584 - Swiping from the top to make the status bar appear in full screen.
Bumping manifests a=b2g-bump