Bumping gaia.json for 3 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/4e4cf0beae7e
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Merge pull request #13702 from AndreiH/bug937660_v1.2

Bug 937660 - Move timezone settings from the setUp into testvars.json

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https://hg.mozilla.org/integration/gaia-1_2/rev/cf58882cdc88
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 937660 - Move timezone settings from the setUp into testvars.json

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https://hg.mozilla.org/integration/gaia-1_2/rev/c83ba7782d1a
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Revert "Bug 934446 - Test Messages contact input validation"

This reverts commit 18fa0b8b421fc3db4f090a7ee673646e7857c994.