Specify exact minimum Go version in go.mod

Starting with Go version 1.21, the exact minimum Go release version or
the toolchain version must be specified in go.mod (see also
golang/go#62278 (comment)). So,
change the Go version from "1.23" to "1.23.0".

Signed-off-by: hwipl <33433250+hwipl@users.noreply.github.com>

go.mod

@@ -1,6 +1,6 @@
 module github.com/telekom-mms/tnd
 
-go 1.23
+go 1.23.0
 
 require (
 	github.com/fsnotify/fsnotify v1.7.0