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

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https://hg.mozilla.org/integration/gaia-central/rev/5ac501412892
Author: Staś Małolepszy <stas@mozilla.com>
Desc: Merge pull request #18684 from stasm/993188-mozL10n.ready-lazy-fix

Bug 993188 - Clean up mozL10n.ready (re-landing). r=gandalf f=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/3687054622b7
Author: Staś Małolepszy <stas@mozilla.com>
Desc: Bug 993188 - Clean up mozL10n.ready (re-landed). r=gandalf f=etienne
Bumping manifests a=b2g-bump