strscan.c: fix typo

* ext/strscan/strscan.c (inspect1): fix typo, rb_str_cat() instead
  of rb_str_cat2().

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44592 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/strscan/strscan.c

@@ -1198,7 +1198,7 @@ inspect1(struct strscanner *p)
 	str = rb_str_new(0, 0);
 	len = p->curr;
     }
-    rb_str_cat2(str, CURPTR(p) - len, len);
+    rb_str_cat(str, CURPTR(p) - len, len);
     return rb_str_dump(str);
 }