tools/testing/selftests/x86/unwind_vdso.c: Remove duplicate header

Remove sys/ucontext.h which is included more than once.
Signed-off-by: Sabyasachi Gupta <sabyasachi.linux@gmail.com>
Signed-off-by: Shuah Khan <shuah@kernel.org>

tools/testing/selftests/x86/unwind_vdso.c

@@ -44,7 +44,6 @@ int main()
 #include <stdbool.h>
 #include <sys/ptrace.h>
 #include <sys/user.h>
-#include <sys/ucontext.h>
 #include <link.h>
 #include <sys/auxv.h>
 #include <dlfcn.h>