Remove unused ol.format.Feature.getExtensions function

src/ol/format/topojson.js

@@ -40,13 +40,6 @@ ol.format.TopoJSON = function(opt_options) {
 ol.inherits(ol.format.TopoJSON, ol.format.JSONFeature);
 
 
-/**
- * @const {Array.<string>}
- * @private
- */
-ol.format.TopoJSON.EXTENSIONS_ = ['.topojson'];
-
-
 /**
  * Concatenate arcs into a coordinate array.
  * @param {Array.<number>} indices Indices of arcs to concatenate.  Negative
@@ -201,14 +194,6 @@ ol.format.TopoJSON.readMultiPolygonGeometry_ = function(object, arcs) {
 };
 
 
-/**
- * @inheritDoc
- */
-ol.format.TopoJSON.prototype.getExtensions = function() {
-  return ol.format.TopoJSON.EXTENSIONS_;
-};
-
-
 /**
  * Create features from a TopoJSON GeometryCollection object.
  *