message: docs: Fix code example in the ChangeDetectorRef docs
  Minor example fix: mark the 'ref' constructor parameter as a private property
diff: @@ -26,7 +26,7 @@ export abstract class ChangeDetectorRef {
  * class Cmp {
  * numberOfTicks = 0;
  *
  - * constructor(ref: ChangeDetectorRef) {
  + * constructor(private ref: ChangeDetectorRef) {
  * setInterval(() => {
  * this.numberOfTicks ++
  * // the following is required, otherwise the view will not be updated
  