How do I correct InnoDB Multiple files found for the same tablespace ID?

Some time ago after an update of Ubuntu 20.10, I discovered that MySQL was not running. When I tried to restart it, the error message suggested that it had started, failed and stopped. A check of the error log contained "InnoDB Multiple files found for the same tablespace ID" and listed 25 such instances, for example Tablespace ID: 92 = ['mercury/pickupcity.ibd', 'mycity/wp_mycity_eventlog.ibd'] How do I correct InnoDB Multiple files found for the same tablespace ID?