Two hard drives after restoring from Time Machine; now I can't back up
I upgraded to Catalina and it was so slow that I decided to restore from a Time Machine backup from the day before the upgrade.
The first time I tried to restore I got an error. The second time I tried to restore, two Macintosh Hard Drives were available to choose from to restore the backup. I chose one and the restore worked fine.
Except now I have two "Macintosh HD" (see photos). Time Machine can't backup because "two of the disks to back up have the same name."
I did not have a partitioned HD before the restore and I'd like to combine them back into the same HD. Question is, can I just delete the second HD by clicking the "-" button? Will that cause me any problems or delete any data that isn't on the other drive?
FYI here is the system information:
iMac Pro