Update spec/Section 3 -- Type System.md

Co-authored-by: Benoit 'BoD' Lubek <[email protected]>

Author: robrichard

spec/Section 3 -- Type System.md

@@ -2230,8 +2230,8 @@ directive @stream(
 
 The `@stream` directive may be provided for a field whose type incorporates a
 `List` type modifier. The directive enables returning a partial list initially,
-followed by additional items in subsequent payloads. Should the field type
-incorporate multiple `List` type modifiers, only the outermost list is streamed.
+followed by additional items in subsequent payloads. If the field type
+incorporates multiple `List` type modifiers, only the outermost list is streamed.
 
 Note: The mechanism through which items are streamed is implementation-defined
 and may use technologies such as asynchronous iterators.