docs(dialog): Fix DialogForm constructor sample (#2144)

closes #2143

Author: trimox

demos/src/app/components/dialog/dialog.ts

@@ -351,7 +351,7 @@ export class DialogScrollable {
   templateUrl: 'dialog-form.html',
 })
 export class DialogForm {
-  constructor(public dialogRef: MdcDialogRef<DialogConfirmation>,
+  constructor(public dialogRef: MdcDialogRef<DialogForm>,
     @Inject(MDC_DIALOG_DATA) public data: DialogData) { }
 
   profileForm = new FormGroup({