set ImageMagic as graphics processor

public/typo3conf/LocalConfiguration.php

@@ -88,7 +88,7 @@ return [
         ],
     ],
     'GFX' => [
-        'processor' => 'GraphicsMagick',
+        'processor' => 'ImageMagick',
         'processor_allowTemporaryMasksAsPng' => false,
         'processor_colorspace' => 'RGB',
         'processor_effects' => false,