Hide skipped tests by default in Differential build result summary view

Summary: Ref T8096. Currently, we hide passing tests by default (they aren't interesting) but should also hide skipped tests by default (they aren't interesting either).

Test Plan: {F694485}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T8096

Differential Revision: https://secure.phabricator.com/D13821