generic explicit method/property overriding in PE

ref https://github.com/FibonacciFox/Peachpie.Avalonia/blob/early-version-peachpie/PeachPie%20Extension%20Libraries/Peachpie.Base.Ext/src/Collections/ObservableCollection.cs

src/Peachpie.CodeAnalysis/Symbols/SubstitutedMethodSymbol.cs

@@ -220,13 +220,7 @@ public override ImmutableArray<TypeSymbol> TypeArguments
             }
         }
 
-        public sealed override MethodSymbol OriginalDefinition
-        {
-            get
-            {
-                return originalDefinition;
-            }
-        }
+        protected override Symbol OriginalSymbolDefinition => originalDefinition;
 
         public sealed override bool IsExtern
         {