Avoid warnings from gcc-16

gcc-16 adds warnings about using strncpy() to copy into a buffer with
  size equal to the max count, possibly creating an unterminated string.
  Since we don't care about the contents here and both buffers are the
  same size, just do a byte copy.

tests/rigctl_parse.c

@@ -1865,7 +1865,7 @@ readline_repeat:
 
         // we need to copy client_version to our thread in case there are multiple client versions
         // client_version is used to determine any backward compatibility requirements or problems
-        strncpy(client_version, rs->client_version, sizeof(client_version));
+        memcpy(client_version, rs->client_version, sizeof(client_version));
     }