copy/paste error in inline docs

[joyously]

In the load_plugin_editor_php function, the inline docs for the filter are incorrect, where it mentions a theme.

/**
 * Give folks a chance to filter the arguments passed to CodeMirror -- This will let them enable
 * or disable it (by returning something that evaluates to false) as they choose as well.
 *
 * @param array    $options The array of options to be passed to CodeMirror. Falsey doesn't use CodeMirror.
 * @param string   $file    The file being displayed.
 * @param WP_Theme $theme   The WP_Theme object for the current theme being edited.
 */
self::$options = apply_filters( 'plugin_editor_codemirror_opts', self::$options, $file, $plugin );