LIMS-1382: Add message to users about using the shipping service

[ndg63276]

JIRA ticket: LIMS-1382

Summary:

Add a short message advising users to fill in the shipping service form in full.

Changes:

• Message added

To test:

• Set $use_shipping_service_redirect = True;
• Go to a shipment that has not accepted the DLS terms, eg from mx23694, click request dispatch, should see full form for dispatch within Synchweb
• Click Use Facility Account, check the form disappears, "Proceed" button appears, and a highlighted message appears
• Change the country to non-UK, check the form re-appears and the message disappears