Simplify default export

This removes unnecessary variable declarations where the default object is an object.

src/ol/source/WMTSRequestEncoding.js

@@ -1,13 +1,12 @@
 /**
  * @module ol/source/WMTSRequestEncoding
  */
+
 /**
  * Request encoding. One of 'KVP', 'REST'.
  * @enum {string}
  */
-var _ol_source_WMTSRequestEncoding_ = {
+export default {
   KVP: 'KVP',  // see spec §8
   REST: 'REST' // see spec §10
 };
-
-export default _ol_source_WMTSRequestEncoding_;