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

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https://hg.mozilla.org/integration/gaia-central/rev/521ec72c1a78
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #18505 from zbraniecki/999195-cleanup-mozl10n-emergency-call

Bug 999195 - Clean up bootstrap mozL10n API use in Emergency Call

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https://hg.mozilla.org/integration/gaia-central/rev/023329bc3261
Author: Zbigniew Braniecki <gandalf@mozilla.com>
Desc: Bug 999195 - Clean up bootstrap mozL10n API use in Emergency Call
Bumping manifests a=b2g-bump