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

========

https://hg.mozilla.org/integration/gaia-central/rev/74ed21fbc313
Author: Ryan VanderMeulen <ryanvm@gmail.com>
Desc: Merge pull request #25456 from lhadji/1087940-build-number

1087940 - Make ro.build.version.incremental available through settings

========

https://hg.mozilla.org/integration/gaia-central/rev/b7e9555aa03e
Author: Leila Hadji <leila.hadji@sonymobile.com>
Desc: 1087940 - Make ro.build.version.incremental available through settings
Bumping manifests a=b2g-bump