test: follow recent ImageMagick spec.

Note that raster image to SVG conversion no longer works without potrace.

bt5/erp5_dms/TestTemplateItem/portal_components/test.erp5.testERP5WebWithDms.py

@@ -831,14 +831,6 @@ return True
                             image_reference + '?format=jpg', credential)
     self.assertEqual(response.getHeader('content-type'), 'image/jpeg')
 
-    # testing Image conversions, svg
-    # disable Image permissiions checks format checks
-    createZODBPythonScript(portal.portal_skins.custom, 'Image_checkConversionFormatPermission',
-                           '**kw', 'return 1')
-    response = self.publish(website.absolute_url_path() + '/' +\
-                            image_reference + '?format=svg', credential)
-    self.assertEqual(response.getHeader('content-type'), 'image/svg+xml')
-
     # testing Image conversions, resizing
     response = self.publish(website.absolute_url_path() + '/' +\
                             image_reference + '?display=large', credential)