src/login.c: Remove dead code

The functions that set these strings --do_rlogin() and login_prompt()--
make sure to terminate them with a NUL.

Fixes: 3704745289 ("* lib/defines.h: Define USER_NAME_MAX_LENGTH, based on utmp and [...]")
Signed-off-by: Alejandro Colomar <alx@kernel.org>

src/login.c

@@ -834,7 +834,6 @@ int main (int argc, char **argv)
 			}
 			preauth_flag = false;
 			username = XMALLOC(max_size, char);
-			username[max_size - 1] = '\0';
 			login_prompt(username, max_size);
 
 			if ('\0' == username[0]) {