Use static call

Author: vmcj

webapp/src/Utils/Utils.php

@@ -408,7 +408,7 @@ public static function apcaContrast(string $fgColor, string $bgColor): float
     /**
      * @return array{string, string}
      */
-    private function hexToForegroundAndBorder(string $rgb): array
+    private static function hexToForegroundAndBorder(string $rgb): array
     {
         $background = Utils::parseHexColor($rgb);