Removing a FILESTREAM windows share after uninstall
I managed to find this answer on Stack Overflow.

https://serverfault.com/questions/543326/how-to-remove-a-windows-share-when-the-folder-does-not-exist-anymore/543350#543350

I removed the MSSQLSERVER share key from the registry at the below path, and rebooted. The share is no longer there in net share in command prompt.

I was able to proceed with my re-installation with FILESTREAM enabled.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Shares