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

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https://hg.mozilla.org/integration/gaia-central/rev/47f28091eeed
Author: Germán Toro del Valle <gtorodelvalle@gmail.com>
Desc: Merge pull request #14581 from gtorodelvalle/contacts-bug-938261-contact-update-activity

Bug 938219 - [Contacts] Unable to select a contact via the contact update activity (r=jmcanterafonseca)

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https://hg.mozilla.org/integration/gaia-central/rev/8c3e597f021a
Author: Germán Toro del Valle <gtorodelvalle@gmail.com>
Desc: Bug 938219 - [Contacts] Unable to select a contact via the contact update activity