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/0edd01975a68
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #15092 from davidflanagan/bug939962v1.2

Bug 939962: manual uplift of willReadFrequently patch to v1.2

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https://hg.mozilla.org/integration/gaia-1_2/rev/da71cd26c0d5
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 939962: manual uplift of willReadFrequently patch to v1.2