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

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https://hg.mozilla.org/integration/gaia-central/rev/31b4142ae6e2
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #21504 from KevinGrandon/bug_1036053_vertical_app_uninstall_pending_test

Bug 1036053 - Intermittent failing test, TEST-UNEXPECTED-FAIL | /builds/slave/test/gaia/apps/verticalhome/test/marionette/app_uninstall_pending_test.js

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https://hg.mozilla.org/integration/gaia-central/rev/38a7d43f99ce
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1036053 - Intermittent failing test, TEST-UNEXPECTED-FAIL | /builds/slave/test/gaia/apps/verticalhome/test/marionette/app_uninstall_pending_test.js r=me
Bumping manifests a=b2g-bump