tweak comment

Author: adolgachev

src/material/form-field/form-field.ts

@@ -308,7 +308,7 @@ export class MatFormField
   // Unique id for the hint label.
   readonly _hintLabelId = this._idGenerator.getId('mat-mdc-hint-');
 
-  // Ids obtained from the fields
+  // Ids obtained from the error and hint fields
   private _describedByIds: string[] | undefined;
 
   /** Gets the current form field control */