Bumping gaia.json for 2 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/fb191b9a5d6c
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #11159 from cctuan/896417

Bug 896417 - Remove mouse_event_shim.js from music app

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https://hg.mozilla.org/integration/gaia-central/rev/50cd8f4b02c8
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 896417 - Remove mouse_event_shim.js from music app