docs(forms): correct sample code for FormArray.reset (#42477)

Remove unexpected this, correct output comment for arr.value and correct parameter type for FormArray.get().

PR Close #42477

packages/forms/src/model.ts

@@ -2091,19 +2091,19 @@ export class FormArray extends AbstractControl {
    * ]);
    * arr.reset(['name', 'last name']);
    *
-   * console.log(this.arr.value);  // ['name', 'last name']
+   * console.log(arr.value);  // ['name', 'last name']
    * ```
    *
    * ### Reset the values in a form array and the disabled status for the first control
    *
    * ```
-   * this.arr.reset([
+   * arr.reset([
    *   {value: 'name', disabled: true},
    *   'last'
    * ]);
    *
-   * console.log(this.arr.value);  // ['name', 'last name']
-   * console.log(this.arr.get(0).status);  // 'DISABLED'
+   * console.log(arr.value);  // ['last']
+   * console.log(arr.at(0).status);  // 'DISABLED'
    * ```
    *
    * @param value Array of values for the controls