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

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https://hg.mozilla.org/integration/gaia-central/rev/505dfe87a4a5
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #20541 from cctuan/973443-2

Bug 973443 - [settings] refactor Display panel with AMD pattern

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https://hg.mozilla.org/integration/gaia-central/rev/5762c343ea1a
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 973443 - [settings] refactor Display panel with AMD pattern
Bumping manifests a=b2g-bump