message: docs(forms): fix grammar and add clarification to setValue docs
  Changed `setValue` documentation for throwing an error as it contained a grammar
  mistake and also may have caused ambiguity around when exactly the
  method would throw.
  PR Close
diff: @@ -1366,7 +1366,7 @@ export class FormGroup extends AbstractControl {
  * ```
  *
  * @throws When strict checks fail, such as setting the value of a control
  - * that doesn't exist or if you excluding the value of a control.
  + * that doesn't exist or if you exclude a value of a control that does exist.
  *
  * @param value The new value for the control that matches the structure of the group.
  * @param options Configuration options that determine how the control propagates changes
  