[AST] Drop unnecessary pass-by-reference from simple_display for ValueDecls.

Author: DougGregor

include/swift/AST/Decl.h

@@ -6650,7 +6650,7 @@ std::pair<DefaultArgumentKind, Type>
 getDefaultArgumentInfo(ValueDecl *source, unsigned Index);
 
 /// Display ValueDecl subclasses.
-void simple_display(llvm::raw_ostream &out, const ValueDecl *&decl);
+void simple_display(llvm::raw_ostream &out, const ValueDecl *decl);
 
 } // end namespace swift
 

lib/AST/Decl.cpp

@@ -5801,7 +5801,7 @@ NominalTypeDecl *TypeOrExtensionDecl::getBaseNominal() const {
 }
 bool TypeOrExtensionDecl::isNull() const { return Decl.isNull(); }
 
-void swift::simple_display(llvm::raw_ostream &out, const ValueDecl *&decl) {
+void swift::simple_display(llvm::raw_ostream &out, const ValueDecl *decl) {
   if (decl) decl->dumpRef(out);
   else out << "(null)";
 }