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

========

https://hg.mozilla.org/integration/gaia-central/rev/7904ca74f118
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #19169 from etiennesegonzac/bug-1009106-edge-tweaks

Bug 1009106 - Tweaking the edge gestures constants to prevent accidental app changes r=alive

========

https://hg.mozilla.org/integration/gaia-central/rev/1cc0618c458d
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 1009106 - Tweaking the edge gestures constants to prevent accidental app changes.
Bumping manifests a=b2g-bump