Revert "Merge pull request #27230 from rintaro/syntaxparsse-rdar55421369"

This reverts commit b09f87594a, reversing
changes made to d0b7ecab00.

tools/libSwiftSyntaxParser/libSwiftSyntaxParser.cpp

@@ -190,10 +190,6 @@ public:
     return getNodeHandler()(&node);
   }
 
-  void discardRecordedNode(OpaqueSyntaxNode node) override {
-    // FIXME: This method should not be called at all.
-  }
-
   std::pair<size_t, OpaqueSyntaxNode>
   lookupNode(size_t lexerOffset, SyntaxKind kind) override {
     auto NodeLookup = getNodeLookup();