Update packages/codemirror-extension/src/index.ts

Co-authored-by: Jason Grout <jasongrout@users.noreply.github.com>

packages/codemirror-extension/src/index.ts

@@ -149,7 +149,7 @@ function activateEditorServices(app: JupyterFrontEnd): IEditorServices {
  */
 function activateCodeMirror(app: JupyterFrontEnd): ICodeMirror {
   return {
-    codemirrorSingleton: () => CodeMirror
+    get CodeMirror() { return CodeMirror }
   };
 }