WebUI: change validator of page size settings

Previously, this configuration field was validated by integer_validator
which only checks that the input is number.
Now new positive_integer_validator can also check that
the inputed number positive.

https://pagure.io/freeipa/issue/6980

Reviewed-By: Felipe Volpone <felipevolpone@gmail.com>

install/ui/src/freeipa/Application_controller.js

@@ -312,7 +312,7 @@ define([
                         $type: 'text',
                         name: 'pagination_size',
                         label: '@i18n:customization.table_pagination',
-                        validators: ['integer']
+                        validators: ['positive_integer']
                     }
                 ]
             });