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

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https://hg.mozilla.org/integration/gaia-central/rev/04670a88b75f
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #17562 from crh0716/974253_v2

Bug 974253 - Set preferred network type on startup based on the user preference r=jaoo

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https://hg.mozilla.org/integration/gaia-central/rev/91262c8a4d8c
Author: Arthur Chen <crh0716@gmail.com>
Desc: Bug 974253 - Set preferred network type on startup based on the user preference
Bumping manifests a=b2g-bump