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

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https://hg.mozilla.org/integration/gaia-central/rev/1262a9127261
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #20780 from zbraniecki/1027480-new-entity-for-contacts-custom-tag

Bug 1027480 - new l10n id for contact's custom tag

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https://hg.mozilla.org/integration/gaia-central/rev/2dd90896a22f
Author: Zbigniew Braniecki <gandalf@mozilla.com>
Desc: Bug 1027480 - new l10n id for contact's custom tag
Bumping manifests a=b2g-bump