Sometimes the Windows 10 setup files remain after installation—and in rare cases—the files become locked, or…just won’t allow you to delete them because of permission issues.
Try this from an admin prompt
takeown /F C:\$Windows.~BT\* /R /A
icacls C:\$Windows.~BT\*.* /T /grant administrators:F
rmdir /S /Q C:\$Windows.~BT\
takeown /F C:\$Windows.~WS\* /R /A
icacls C:\$Windows.~WS\*.* /T /grant administrators:F
rmdir /S /Q C:\$Windows.~WS\
You can also rename the folder, if you need to begin a new setup, while keeping the original setup files.