zdtm/autofs: don't include bits/signum.h

It isn't required and it is absant on alpine
autofs.c:9:25: fatal error: bits/signum.h: No such file or directory
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

test/zdtm/static/autofs.c

@@ -6,8 +6,6 @@
 #include <string.h>
 #include <signal.h>
 
-#include <bits/signum.h>
-
 #include <sys/wait.h>
 #include <sys/vfs.h>
 #include <sys/mount.h>