[NFC] Correct code blocks in property wrapper doc comments

Author: hborla

include/swift/AST/Decl.h

@@ -5235,7 +5235,7 @@ class VarDecl : public AbstractStorageDecl {
   ///
   /// \code
   /// @Lazy var i = 17
-  /// \end
+  /// \endcode
   ///
   /// Or when there is no initializer but each composed property wrapper has
   /// a suitable `init(wrappedValue:)`.

include/swift/AST/PropertyWrappers.h

@@ -141,7 +141,7 @@ struct PropertyWrapperBackingPropertyInfo {
   ///
   /// \code
   /// @Lazy var i = 17
-  /// \end
+  /// \endcode
   ///
   /// This is the specified initial value (\c 17), which is suitable for
   /// embedding in the expression \c initializeFromOriginal.