7 files declare their use of SearchApiPluginManager in Search API 8

BackendPluginManager.php in src/Backend/BackendPluginManager.php

DatasourcePluginManager.php in src/Datasource/DatasourcePluginManager.php

DataTypePluginManager.php in src/DataType/DataTypePluginManager.php

DisplayPluginManager.php in src/Display/DisplayPluginManager.php

ParseModePluginManager.php in src/ParseMode/ParseModePluginManager.php

ProcessorPluginManager.php in src/Processor/ProcessorPluginManager.php

TrackerPluginManager.php in src/Tracker/TrackerPluginManager.php