remove unused use statements

plugins/ImageGraph/StaticGraph.php

plugins/Installation/FormFirstWebsiteSetup.php

plugins/Installation/Installation.php

plugins/LanguagesManager/Commands/TranslationBase.php

plugins/Live/Visitor.php

plugins/Live/tests/System/APITest.php

plugins/MultiSites/API.php

plugins/MultiSites/Controller.php

plugins/Referrers/Social.php

.../Referrers/tests/Integration/Columns/ReferrerNameTest.php

plugins/Referrers/tests/Unit/ReferrersTest.php

plugins/ScheduledReports/API.php

plugins/ScheduledReports/Controller.php

plugins/ScheduledReports/Model.php

plugins/ScheduledReports/tests/Integration/ApiTest.php

plugins/SegmentEditor/API.php

plugins/SegmentEditor/SegmentEditor.php

.../SegmentEditor/tests/Integration/SegmentFormatterTest.php

plugins/SitesManager/Controller.php

plugins/SitesManager/tests/Integration/SitesManagerTest.php