iucvterm/tests: Remove unused termio.h

The inclusion of termio.h leads to the following compilation error:

  CC          iucvterm/tests/test_functions.o
test_functions.c:16:10: fatal error: termio.h: No such file or directory
   16 | #include <termio.h>
      |          ^~~~~~~~~~

The termio ioctl interface has been obsolete for a very long time and
was replaced by termios. termio.h was still present for compatibility
but was removed with glibc 2.42.
iucvterm uses termios.h correctly in the tool. The test however not only
includes termio.h erroneously, it doesn't even require it. Remove the
inclusion of termio.h.

Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

iucvterm/test/test_functions.c

@@ -13,7 +13,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/ioctl.h>
-#include <termio.h>
 #include <unistd.h>
 
 #include "iucvterm/functions.h"