Fix typo in helpers.ts (microsoft#45365)

funtions

Author: Ikko Ashimine

src/services/refactors/helpers.ts

@@ -1,7 +1,7 @@
 /* @internal */
 namespace ts.refactor {
     /**
-     * Returned by refactor funtions when some error message needs to be surfaced to users.
+     * Returned by refactor functions when some error message needs to be surfaced to users.
      */
     export interface RefactorErrorInfo {
         error: string;
@@ -22,4 +22,4 @@ namespace ts.refactor {
         if(!requested) return true;
         return known.substr(0, requested.length) === requested;
     }
-}
+}