docs(forms): move extended text to @usageNotes (#26039)

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PR Close #26039

packages/forms/src/validators.ts

@@ -22,12 +22,12 @@ function isEmptyInputValue(value: any): boolean {
  * An `InjectionToken` for registering additional synchronous validators used with `AbstractControl`s.
  *
  * @see `NG_ASYNC_VALIDATORS`
- * 
+ *
  * @usageNotes
- * 
+ *
  * ### Providing a custom validator
- * 
- * The following example registers a custom validator directive. Adding the validator to the 
+ *
+ * The following example registers a custom validator directive. Adding the validator to the
  * existing collection of validators requires the `multi: true` option.
  *
  * ```typescript
@@ -50,7 +50,7 @@ export const NG_VALIDATORS = new InjectionToken<Array<Validator|Function>>('NgVa
  * An `InjectionToken` for registering additional asynchronous validators used with `AbstractControl`s.
  *
  * @see `NG_VALIDATORS`
- * 
+ *
  */
 export const NG_ASYNC_VALIDATORS =
     new InjectionToken<Array<Validator|Function>>('NgAsyncValidators');
@@ -64,7 +64,7 @@ const EMAIL_REGEXP =
  *
  * A validator is a function that processes a `FormControl` or collection of
  * controls and returns an error map or null. A null map means that validation has passed.
- * 
+ *
  * @see [Form Validation](/guide/form-validation)
  *
  */
@@ -322,7 +322,7 @@ export class Validators {
    * @description
    * Validator that performs no operation.
    */
-  static nullValidator(c: AbstractControl): ValidationErrors|null { return null; }
+  static nullValidator(control: AbstractControl): ValidationErrors|null { return null; }
 
   /**
    * @description