Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_4/rev/494e0e747607
Author: Maliha-Momtaz-Islam <malihaislam81@gmail.com>
Desc: Bug 1072458 - Certain characters cannot be input using Bangla keyboard

(cherry picked from commit 707c14abb8dc8046c9dcbeef25b59a331635c34f)

Conflicts:
	apps/keyboard/js/layouts/bn-Avro.js
a=bajaj.

(cherry picked from commit 5616d86d52970bae0fdc65eaf7db97360172e750)
Bumping manifests a=b2g-bump