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

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https://hg.mozilla.org/integration/gaia-central/rev/aff9f1707f87
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...

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https://hg.mozilla.org/integration/gaia-central/rev/02e03d210e37
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 939962: attempt to reduce memory requirements for saving an edited image