libc: update kernel library references

lib/libc/io/stdio/fclose.c

@@ -2,7 +2,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
-#include <mango/log.h>
+#include <magenta/log.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>