expand: Remove unused includes

sys/sysctl.h is deprecated on glibc, so it leads to warnings.
According to fa4ec55c96, it was included for KERN_PROCARGS2 for
process expansion, but process expansion is gone, so it's unused now.

(there is another use of it in common.cpp, but that's only on FreeBSD)

Also 1f06e5f0b9ee483053b987c9cab9f1f5fce2590 only included
tokenizer.h (present since the initial commit) if KERN_PROCARGS2
wasn't available, so it can't have been important.

This builds and passes the tests on:

- Archlinux, with glibc 2.30
- Alpine, with musl
- FreeBSD
- NetBSD

src/expand.cpp

@@ -13,9 +13,6 @@
 #include <cstring>
 #include <cwchar>
 
-#ifdef HAVE_SYS_SYSCTL_H
-#include <sys/sysctl.h>  // IWYU pragma: keep
-#endif
 #ifdef SunOS
 #include <procfs.h>
 #endif
@@ -51,10 +48,6 @@
 #include "wcstringutil.h"
 #include "wildcard.h"
 #include "wutil.h"  // IWYU pragma: keep
-#ifdef KERN_PROCARGS2
-#else
-#include "tokenizer.h"
-#endif
 
 /// Characters which make a string unclean if they are the first character of the string. See \c
 /// expand_is_clean().