Add explicit offset

Fixes vimeo#4202

src/Psalm/Internal/Stubs/CoreGenericFunctions.phpstub

@@ -667,7 +667,7 @@ function preg_replace_callback($search, $replace, $subject, int $limit = -1, &$c
  *        ) $matches
  * @return int
  */
-function preg_match_all($pattern, $replace, &$matches = [], int $flags = 1) {}
+function preg_match_all($pattern, $replace, &$matches = [], int $flags = 1, int $offset = 0) {}
 
 /**
  * @psalm-pure