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/7466402c1485
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #14474 from davidflanagan/bug939962-v1.2

Merge pull request #13887 from davidflanagan/bug939962

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https://hg.mozilla.org/integration/gaia-1_2/rev/d73a38bad9ea
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #13887 from davidflanagan/bug939962

Bug 939962: attempt to reduce memory requirements for saving an edited i...(cherry picked from commit 08d96ee9678bef48a4540470ed96d32e962ff557)