db.veal typo fix

Author: Sam Kleinman

source/reference/limits.txt

@@ -91,7 +91,7 @@ Limits
    The :dbcommand:`group` does not work with sharding. Use
    :dbcommand:`mapreduce` or :dbcommand:`aggregate` instead.
 
-   :func:`db.veal()` is incompatible with sharded collections. You may
+   :func:`db.eval()` is incompatible with sharded collections. You may
    use :func:`db.eval()` with un-sharded collections in a shard
    cluster.