dist: Fully lock the tss system user

Use the `u!` notation to fully lock the system user.
It is highly unlikely that the `tss` user should ever be logged into
(e.g. via SSH).

This sysusers.d feature has been released with systemd 257 on
2024-12-10.

Related-to: https://github.com/systemd/systemd/releases/tag/v257
Signed-off-by: David Runge <dave@sleepmap.de>

Author: dvzrv

dist/sysusers.d/tpm2-tss.conf

@@ -1,2 +1,2 @@
 #Type Name ID GECOS               Home directory Shell
-u     tss  -  "tss user for tpm2"
+u!     tss  -  "tss user for tpm2"