Removing deprecated renderMode reference in playground. (#3107)

tests/playground.html

@@ -71,8 +71,6 @@
 var workspace = null;
 
 function start() {
-  // TODO (#2702): Choose an API for picking the renderer.
-  Blockly.renderMode = 'compatibility';
   setBackgroundColour();
 
   // Parse the URL arguments.

tests/screenshot/playground_new.html

@@ -35,12 +35,6 @@ limitations under the License.
 <script src="../../blocks/procedures.js"></script>
 <script src="../blocks/test_blocks.js"></script>
 
-<script>
-  function start() {
-    // TODO (#2702): Choose an API for picking the renderer.
-    Blockly.renderMode = 'compatibility';
-  }
-</script>
 <style>
 html, body {
   height: 100%;