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

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https://hg.mozilla.org/integration/gaia-central/rev/ec8bcb494172
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #18335 from yzen/bug-994702

Bug 994702 - making an incorectly visible callscreen 'hold' text an aria...

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https://hg.mozilla.org/integration/gaia-central/rev/7e0d7ac4e26c
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 994702 - making an incorrectly visible callscreen 'hold' text an aria label. r=Rik

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https://hg.mozilla.org/integration/gaia-central/rev/7b732b3e19c5
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #18157 from gasolin/issue-993318

Bug 993318 - [Settings] build script improvement for load time, r=arthur

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https://hg.mozilla.org/integration/gaia-central/rev/fa427e31dfab
Author: gasolin <gasolin@gmail.com>
Desc: Bug 993318 - [Settings] build script improvement for load time

- prompt to alameda 0.2
Bumping manifests a=b2g-bump