trivial: fix UL formatting

Author: andf-mongodb

source/reference/operator/aggregation/lookup.txt

@@ -618,10 +618,11 @@ collection for equality matches. For example, if the index
 ``{ stock_item: 1, instock: 1 }`` exists on the ``warehouses``
 collection:
 
-   - The equality match on the ``warehouses.stock_item`` field uses the
-     index.
-   - The range part of the query on the ``warehouses.instock`` field
-     does not use the indexed field in the compound index.
+- The equality match on the ``warehouses.stock_item`` field uses the
+  index.
+
+- The range part of the query on the ``warehouses.instock`` field
+  does not use the indexed field in the compound index.
 
 .. seealso::