Clean up user-rooms-api-tests.js
Remove unnecessary invocation of 'ensureIntegrationEnvironment`.
Forgotten item from https://dev.gitlab.org/gitlab/gitter/webapp/merge_requests/25#note_183939
Remove unnecessary invocation of 'ensureIntegrationEnvironment`.
Forgotten item from https://dev.gitlab.org/gitlab/gitter/webapp/merge_requests/25#note_183939