LibC: Unconditionally include bits/posix1_lim.h from limits.h

No other system seems to put this behind a _USE_POSIX ifdef.

Userland/Libraries/LibC/limits.h

@@ -92,6 +92,4 @@
 
 #define TZNAME_MAX 64
 
-#ifdef __USE_POSIX
-#    include <bits/posix1_lim.h>
-#endif
+#include <bits/posix1_lim.h>