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

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https://hg.mozilla.org/integration/gaia-central/rev/6ce5c1528861
Author: Guillaume C. Marty <gmarty@users.noreply.github.com>
Desc: Merge pull request #25578 from gmarty/Bug-1078727-Marionette-tests

Bug 1078727 - Adding Marionette tests

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https://hg.mozilla.org/integration/gaia-central/rev/0226054e14ba
Author: Guillaume Marty <edo999@gmail.com>
Desc: Bug 1078727 - Adding Marionette tests
Bumping manifests a=b2g-bump