Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/e1845bb40c44
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1049137 - Disable intermittent failing test, TEST-UNEXPECTED-FAIL | /builds/slave/test/gaia/apps/system/test/marionette/app_usage_metrics_test.js | App Usage Metrics > Uninstalled apps are counted
Bumping manifests a=b2g-bump