Remove PruneWebHookLogsWorker class

What does this MR do?

It removes the PruneWebHookLogsWorker class. The worker was used as a cronjob to remove old logs from the WebHookLogs table. The cron job got deactivated in !59120 (merged) because old logs will be removed by a partition table &5558 (closed)

No changelog entry because this is not a user facing change.

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)

Related to #327613 (closed)