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

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https://hg.mozilla.org/integration/gaia-central/rev/bd57e387637d
Author: lissyx <lissyx+github@lissyx.dyndns.org>
Desc: Merge pull request #20572 from lissyx/bug1025149

Bug 1025149 - Stop AppWindow events under kill() r=etienne_s

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https://hg.mozilla.org/integration/gaia-central/rev/a7abc44dbf77
Author: Alexandre Lissy <lissyx+github@lissyx.dyndns.org>
Desc: Bug 1025149 - Stop AppWindow events under kill() r=etienne_s
Bumping manifests a=b2g-bump