[CodeMirror] removed is actually a list of string.

as is test on the same object.

codemirror/codemirror.d.ts

@@ -600,7 +600,7 @@ declare module CodeMirror {
         /** Array of strings representing the text that replaced the changed range (split by line). */
         text: string[];
         /**  Text that used to be between from and to, which is overwritten by this change. */
-        removed: string;
+        removed: string[];
         /**  String representing the origin of the change event and wether it can be merged with history */
         origin: string;
     }