Update screenshot format examples in config (#206)

In the screenshot configuration of the utility settings, the example values for the screenshot format are updated to simple file extensions 'jpg', 'png', and 'webp', instead of the MIME types.

src/Resources/config/definition/utils/screenshots.php

@@ -49,7 +49,7 @@ function getScreenshotsNode(string $info): ArrayNodeDefinition
         ->end()
         ->scalarNode('format')
         ->info('The format of the screenshot. Will convert the file if set.')
-        ->example(['image/jpg', 'image/png', 'image/webp'])
+        ->example(['jpg', 'png', 'webp'])
         ->end()
         ->scalarNode('reference')
             ->defaultNull()