Editorial: widen parameter type of IsAnonymousFunctionDefinition (tc3…

…9#3148)

Among the 16 call sites of IsAnonymousFunctionDefinition, one of them in
NamedEvaluation of ParenthesizedExpression : `(` Expression `)` passes
|Expression| Parse Node which was not covered in the previous type
annotation. This commit fixes this issue.

spec.html

@@ -8990,7 +8990,7 @@ <h1>Static Semantics: IsFunctionDefinition ( ): a Boolean</h1>
     <emu-clause id="sec-isanonymousfunctiondefinition" type="abstract operation">
       <h1>
         Static Semantics: IsAnonymousFunctionDefinition (
-          _expr_: an |AssignmentExpression| Parse Node or an |Initializer| Parse Node,
+          _expr_: an |AssignmentExpression| Parse Node, an |Initializer| Parse Node, or an |Expression| Parse Node,
         ): a Boolean
       </h1>
       <dl class="header">