Docs: Correct documentation for the_password_form hook.

This replaces an outdated note about the 20 characters limit on the password field in the WordPress database schema.

The `post_password` column was increased to 255 characters in WordPress 4.7.

Follow-up to [27676], [38590].

Props debarghyabanerjee, peterwilsoncc, dd32, mukesh27.
Fixes #61703.

git-svn-id: https://develop.svn.wordpress.org/trunk@58846 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/post-template.php

@@ -1777,9 +1777,10 @@ function get_the_password_form( $post = 0 ) {
 	/**
 	 * Filters the HTML output for the protected post password form.
 	 *
-	 * If modifying the password field, please note that the core database schema
-	 * limits the password field to 20 characters regardless of the value of the
-	 * size attribute in the form input.
+	 * If modifying the password field, please note that the WordPress database schema
+	 * limits the password field to 255 characters regardless of the value of the
+	 * `minlength` or `maxlength` attributes or other validation that may be added to
+	 * the input.
 	 *
 	 * @since 2.7.0
 	 * @since 5.8.0 Added the `$post` parameter.