docs: add @phpstan-var to stop rector to skip RemoveAlwaysTrueIfCondi…

…tionRector

Without this doc type, Rector will refactor the following:
1) system/Router/AutoRouterImproved.php:294

    ---------- begin diff ----------
@@ @@

             // Update the positions.
             $this->methodPos = $this->paramPos;
-            if ($params === []) {
-                $this->paramPos = null;
-            }
+            $this->paramPos = null;
             if ($this->paramPos !== null) {
                 $this->paramPos++;
             }
    ----------- end diff -----------

Applied rules:
 * RemoveAlwaysTrueIfConditionRector

system/Router/AutoRouterImproved.php

@@ -46,6 +46,8 @@ final class AutoRouterImproved implements AutoRouterInterface
 
     /**
      * An array of params to the controller method.
+     *
+     * @phpstan-var list<string>
      */
     private array $params = [];
 
@@ -72,6 +74,8 @@ final class AutoRouterImproved implements AutoRouterInterface
 
     /**
      * The URI segments.
+     *
+     * @phpstan-var list<string>
      */
     private array $segments = [];
 
@@ -279,6 +283,7 @@ public function getRoute(string $uri, string $httpVerb): array
         }
 
         // The first item may be a method name.
+        /** @phpstan-var list<string> $params */
         $params = $this->params;
 
         $methodParam = array_shift($params);