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

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https://hg.mozilla.org/integration/gaia-1_3/rev/88318d7821be
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #20093 from davidflanagan/bug1020002-v1.3

Bug1020002 v1.3

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https://hg.mozilla.org/integration/gaia-1_3/rev/73f8e881f085
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 1020002: don't allow an activity choice that could subvert forward-lock
Bumping manifests a=b2g-bump