Clarify why multiple modifiers can be parsed. Fix conflicts.

Author: TysonAndre

tests/cases/parser/parameterPromotion2.php

@@ -1,6 +1,6 @@
 <?php
 class X {
-    // It's a syntax error to have more than one visibility modifier
+    // Starting in php 8.1, it is a compile error rather than a syntax error to have more than one visibility modifier
     public function __construct(
         public protected $var
     ) {}

tests/cases/parser81/intersection_type.php.tree

@@ -34,6 +34,7 @@
                                     "Parameter": {
                                         "attributes": null,
                                         "visibilityToken": null,
+                                        "modifiers": null,
                                         "questionToken": null,
                                         "typeDeclarationList": {
                                             "QualifiedNameList": {
@@ -103,6 +104,7 @@
                                     "Parameter": {
                                         "attributes": null,
                                         "visibilityToken": null,
+                                        "modifiers": null,
                                         "questionToken": null,
                                         "typeDeclarationList": {
                                             "QualifiedNameList": {