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

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https://hg.mozilla.org/integration/gaia-central/rev/06f421c85598
Author: Staś Małolepszy <stas@mozilla.com>
Desc: Merge pull request #18680 from stasm/1000895-system-once-ready

Bug 1000895 - Clean up bootstrap mozL10n API use in System. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/02b56dd9e7f4
Author: Staś Małolepszy <stas@mozilla.com>
Desc: Bug 1000895 - Clean up bootstrap mozL10n API use in System. r=alive
Bumping manifests a=b2g-bump