fixup re introducing "subject Parse Node"

spec.html

@@ -896,7 +896,7 @@ <h1>Syntax-Directed Operations</h1>
 
       <emu-clause id="sec-invoking-syntax-directed-operations">
         <h1>Invoking Syntax-Directed Operations</h1>
-        <p>Syntax-directed operations are invoked with a Parse Node and, optionally, other parameters by using the conventions on steps <emu-xref href="#step-sdo-invocation-example-1"></emu-xref>, <emu-xref href="#step-sdo-invocation-example-2"></emu-xref>, and <emu-xref href="#step-sdo-invocation-example-3"></emu-xref> in the following algorithm:</p>
+        <p>Syntax-directed operations are invoked with a Parse Node (referred to below as “the subject Parse Node”) and, optionally, other parameters. Invocations use the conventions on steps <emu-xref href="#step-sdo-invocation-example-1"></emu-xref>, <emu-xref href="#step-sdo-invocation-example-2"></emu-xref>, and <emu-xref href="#step-sdo-invocation-example-3"></emu-xref> in the following algorithm:</p>
         <emu-alg example>
           1. [id="step-sdo-invocation-example-1"] Let _status_ be SyntaxDirectedOperation of |SomeNonTerminal|.
           1. Let _someParseNode_ be the parse of some source text.