8 files declare their use of ServiceBase in Purge 8.3

DiagnosticsService.php in src/Plugin/Purge/DiagnosticCheck/DiagnosticsService.php

InvalidationsService.php in src/Plugin/Purge/Invalidation/InvalidationsService.php

ProcessorsService.php in src/Plugin/Purge/Processor/ProcessorsService.php

PurgersService.php in src/Plugin/Purge/Purger/PurgersService.php

QueuersService.php in src/Plugin/Purge/Queuer/QueuersService.php

QueueService.php in src/Plugin/Purge/Queue/QueueService.php

ServiceTestTrait.php in tests/src/Traits/ServiceTestTrait.php

TagsHeadersService.php in src/Plugin/Purge/TagsHeader/TagsHeadersService.php