Bug 32355: Add css class url to URL syspref

Bug 32355: Add css class url to URL syspref

Add missing css class to URL syspref.

To Test:
1 - open admin/preferences.pl
2 - Search for URL
3 - casServerUrl, UsageStatsLibraryUrl, KohaManualBaseURL,
    PrivacyPolicyURL, LibrisURL input field size are small.
4 - Apply patch
5 - all URL fields have the same bigger size.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>