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

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https://hg.mozilla.org/integration/gaia-central/rev/8b749da3986f
Author: Wilson Page <wilsonpage@me.com>
Desc: Merge pull request #17755 from wilsonpage/bug/989295

Bug 989295 - [Camera] Fix SettingsController test breaking TBPL

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https://hg.mozilla.org/integration/gaia-central/rev/d17d42feab93
Author: Wilson Page <wilsonpage@me.com>
Desc: Bug 989295 - [Camera] Fix SettingsController test breaking TBPL
Bumping manifests a=b2g-bump