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

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https://hg.mozilla.org/integration/gaia-central/rev/73923a35d9de
Author: Germán Toro del Valle <gtorodelvalle@gmail.com>
Desc: Merge pull request #12269 from gtorodelvalle/dialer-bug-910188-closing-contact-list

Dialer bug 910188 closing contact list (r=jmcanterafonseca)

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https://hg.mozilla.org/integration/gaia-central/rev/32e97206d1dc
Author: Germán Toro del Valle <gtorodelvalle@gmail.com>
Desc: Bug 910188 - [CONTACTS] In export contacts option, if we tap on 'x' button, we come back to Settings screen.