fix: exclude legacy Guzzle6AuthHandler and drop stale phpstan ignore

Author: GrahamCampbell

phpstan.neon.dist

@@ -3,11 +3,7 @@ parameters:
     level: 5
     paths:
     - src
-    ignoreErrors:
-        # On Guzzle 7 the base RequestException has getResponse(), so the
-        # method_exists() guard is statically true; it stays for the Guzzle 8
-        # code path, where the response lives only on the ResponseException
-        # subclass.
-        -
-            message: '#^Call to function method_exists\(\) with GuzzleHttp\\Exception\\RequestException and ''getResponse'' will always evaluate to true\.$#'
-            path: src/Http/REST.php
+    excludePaths:
+        # Legacy, unused Guzzle 6 auth handler retained for backwards
+        # compatibility only; it relies on APIs removed in Guzzle 8.
+        - src/AuthHandler/Guzzle6AuthHandler.php