Bug 41142: Update jQuery-validate plugin to 1.21.0

This patch updates the jQuery validation plugin in both the staff
interface and the OPAC to the latest version, 1.21.0.

To test, apply the patch and clear your browser cache if necessary.

Test various pages in the staff client to confirm that form validation
works as expected:

 - Patron password change form:
   - Password must conform to minPasswordLength
   - Password must not contain leading/trailing spaces
   - Passwords must match

 - Administration -> Add or edit budget:
   - Description, start date, and end date are required
   - Start date must be before end date

 - Administration -> Add or edit Z39.50/SRU server:
   - Server name, hostname, port, and database are required
   - Port, rank, and timeout must be a number

Perform the same check of the "Change password" form in the OPAC.

Sponsored-by: Athens County Public Libraries
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@openfifth.co.uk>
Signed-off-by: Laura Escamilla <laura.escamilla@bywatersolutions.com>

koha-tmpl/intranet-tmpl/prog/en/modules/about.tt

@@ -1138,7 +1138,7 @@
         </p>
 
         <h2>jQuery Validation Plugin</h2>
-        <p> <a href="https://jqueryvalidation.org/">jQuery Validation Plugin v1.19.3</a>: <a href="https://github.com/jquery-validation/jquery-validation/blob/1.19.3/LICENSE.md">MIT License</a> </p>
+        <p> <a href="https://jqueryvalidation.org/">jQuery Validation Plugin v1.21.0</a>: <a href="https://github.com/jquery-validation/jquery-validation/blob/1.21.0/LICENSE.md">MIT License</a> </p>
 
         <h2>JS-YAML</h2>
         <p> <a href="https://nodeca.github.io/js-yaml/">JS-YAML v3.13.1</a>: <a href="https://github.com/nodeca/js-yaml/blob/3.13.1/LICENSE">MIT License</a> </p>