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

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https://hg.mozilla.org/integration/gaia-1_4/rev/abd228ad4cbe
Author: Diego Marcos <diego.marcos@gmail.com>
Desc: Merge pull request #18803 from dmarcos/bug965486v1.4

Bug 965486 - [Camera] Build time configuration system

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https://hg.mozilla.org/integration/gaia-1_4/rev/2f50bc92f4e2
Author: Diego Marcos <diego.marcos@gmail.com>
Desc: Bug 965486 - [Camera] Build time configuration system

It allows to specify an external js/config/app.js file.
The file is copied over the original one in the repo
Bumping manifests a=b2g-bump