Fixes mispelled 'thel.' to 'them.' in mkosi.md.
set to `none`, shim and MokManager will not be installed to the ESP.
If set to `unsigned`, mkosi will search for unsigned shim and
MokManager EFI binaries and install them. If `SecureBoot=` is enabled,
- mkosi will sign the unsigned EFI binaries before installing thel. If
+ mkosi will sign the unsigned EFI binaries before installing them. If
set to `signed`, mkosi will search for signed EFI binaries and install
those. Even if `SecureBoot=` is enabled, mkosi won't sign these
binaries again.