Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/c61922d00c89
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #23897 from gasolin/issue-973445-4

Bug 973445 - [settings] refactor Sound panel with AMD pattern, r=arthur

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https://hg.mozilla.org/integration/gaia-central/rev/d67b5277ca4e
Author: gasolin <gasolin@gmail.com>
Desc: Bug 973445 - [settings] refactor Sound panel with AMD pattern

- use promise
- modulize slider_handler

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https://hg.mozilla.org/integration/gaia-central/rev/fd69f23be436
Author: Carsten Book <tomcat@mozilla.com>
Desc: Merge pull request #25007 from eliperelman/bug-1070615-manual

Bug 1070615 - Manual performance test for start of system app. r=kgrandon

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https://hg.mozilla.org/integration/gaia-central/rev/859ba606b626
Author: Eli Perelman <eli@eliperelman.com>
Desc: Bug 1070615 - Manual performance test for start of system app
Bumping manifests a=b2g-bump