Drop unnecesary config manipulation

islandora_fits.install

@@ -25,15 +25,4 @@ function islandora_fits_install() {
       'field_external_uri' => ['uri' => 'https://projects.iq.harvard.edu/fits'],
     ])->save();
   }
-  // Add xml extension if it doesn't already exist.
-  $field = FieldConfig::load("media.file.field_media_file");
-  if ($field) {
-    $fieldSettings = $field->getSettings();
-    $extensions = $fieldSettings['file_extensions'];
-    if (!strpos($extensions, 'xml')) {
-      $fieldSettings['file_extensions'] .= ' xml';
-      $field->set('settings', $fieldSettings);
-      $field->save();
-    }
-  }
 }