Bumping gaia.json for 2 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/2c9ca6c1834a
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #12756 from arcturus/bug-924890

Bug 924890 - [Contacts] Javascript error after landing bug 902873 (merge error)(cherry picked from commit f4514d1de0d008eda71f9784e78798bf8ad09110)

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https://hg.mozilla.org/integration/gaia-1_2/rev/4685c111bcee
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #12591 from arcturus/contacts-select-perf-1

Bug 902873 - [Contacts] Performance improvements when selecting in contact list(cherry picked from commit c4412deb4fbbae5baefb10abeac1c9bd729606e3)

Conflicts:
	apps/communications/contacts/js/views/list.js