Corrected lone operation specification

Author: frankleonrose

spec/Section 5 -- Validation.md

@@ -143,7 +143,9 @@ mutation dogOperation {
 ** Formal Specification **
 
   * Let {operations} be all operation definitions in the document.
-  * {operations} must be a set of one.
+  * Let {anonymous} be all anonymous operation definitions in the document.
+  * If {operations} is a set of more than 1:
+    * {anonymous} must be empty.
 
 ** Explanatory Text **