Downgrade PHPStan level to 4

[MAILPOET-1915]

RoboFile.php

@@ -378,7 +378,7 @@ class RoboFile extends \Robo\Tasks {
         'php -d memory_limit=2G '.
         "$dir/phpstan.phar analyse ".
         "--configuration $dir/tasks/phpstan/phpstan.neon ".
-        '--level 5 '.
+        '--level 4 '.
         "$dir/lib"
       )
       ->dir(__DIR__ . '/tasks/phpstan')

lib/Subscribers/ImportExport/Import/MailChimp.php

@@ -87,7 +87,7 @@ class MailChimp {
             }
             if (!isset($header_hash)) {
               $header_hash = md5(implode(',', $header));
-            } elseif (md5(implode(',', $header)) !== $header_hash) {
+            } elseif (md5(implode(',', $header) !== $header_hash)) {
               return $this->throwException('headers');
             }
           } else {

tasks/phpstan/phpstan.neon

@@ -7,6 +7,7 @@ parameters:
     - '#Call to an undefined method IdiormResultSet::set()#'
     - '#Argument of an invalid type pQuery\\IQuery supplied for foreach, only iterables are supported#'
     - '#Parameter \#2 \$prefix of function http_build_query expects string, null given.#'
+    - '#Parameter \#1 \$function of function call_user_func_array expects callable(): mixed, .wc_.*. given.#'
   reportUnmatchedIgnoredErrors: false
   dynamicConstantNames:
     - WP_DEBUG