Partitioning: Drop non-partitioned web_hook_logs table

As the final step of partitioning the web_hook_logs table (&5558 (closed)), we'll remove the non-partitioned archive table.

It will follow the successful swap of the base web_hook_logs table with the partitioned copy (#323677 (closed)), after monitoring for a period of time that it caused no issues. It may be released in the same milestone as #323677 (closed) are, at worst case scenario, in the milestone that follows it.