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

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https://hg.mozilla.org/integration/gaia-central/rev/4b7b6c601700
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #25063 from julienw/1081684-load-default-theme-when-a-theme-is-requested

Bug 1081684 - [Build] Themes don't load when running in Firefox r=ricky

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https://hg.mozilla.org/integration/gaia-central/rev/cb41b65ca894
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 1081684 - [Build] Themes don't load when running in Firefox r=ricky
Bumping manifests a=b2g-bump