The err_cleanup() funtion is internal so shouldn't be exported

Running a "make update" wanted to add err_cleanup to libcrypto.num which
is wrong.

Reviewed-by: Richard Levitte <levitte@openssl.org>

include/internal/err.h

@@ -59,6 +59,5 @@
 # define INTERNAL_ERR_H
 
 void err_free_strings_int(void);
-void err_cleanup(void);
 
 #endif