Bug 37846: Fix serial prediction pattern layout

Bug 37846: Fix serial prediction pattern layout

This patch corrects the class which is added to the serial prediction
pattern in order for it to display as a second column in the
subscription edit page. "col-xs-*" classes no longer exist in Bootstrap
5.

To test, apply the patch and go to Serials.

1. Click "New subscription"
2. Enter a record number in the form (e.g. 55)
3. Click "Next" (and confirm there is no vendor)
4. Enter values for
   - First issue publication date
   - Frequency
   - Subscription length
   - Subscription start date
   - Numbering pattern
   - Numbering "Begins with"
5. Click "Test prediction pattern"
   - The prediction pattern panel should appear as a second column on
     the page.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>