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

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https://hg.mozilla.org/integration/gaia-central/rev/40d2ed7f4f61
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #14870 from gasolin/issue-952244

Bug 952244 - Remember my choice is showing up again on gUM audio permiss..., r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/c887f0896311
Author: gasolin <gasolin@gmail.com>
Desc: Bug 952244 - Remember my choice is showing up again on gUM audio permission prompts

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https://hg.mozilla.org/integration/gaia-central/rev/5754a3bfa3f2
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #14938 from gasolin/issue-952940

Bug 952940 - Remove duplicate .chrome > .navigation definition, r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/981d8b181b00
Author: gasolin <gasolin@gmail.com>
Desc: Bug 952940 - Remove duplicate .chrome > .navigation definition