unistd.h: don't include sys/capability.h

Don't pull in unnecessary header files. AFAIK, I've fixed all
the code which didn't include the correct header files.

Change-Id: If0b7bba74e77cb24a0cf9ce8968aa07400855e58
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 97208a0..98970ae 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -33,7 +33,6 @@
 #include <sys/types.h>
 #include <sys/select.h>
 #include <sys/sysconf.h>
-#include <sys/capability.h> /* TODO: Remove this include */
 #include <pathconf.h>
 
 __BEGIN_DECLS