Update error message for deleting an individual when social relationships are present

[goddesswarship]

Expected behavior
When a marked individual (individuals.jsp) has only one associated encounter and a social relationship is present, removing the Identity from the encounter page will prompt the user to delete the social relationship before the individual is deleted.

Current behavior
When an individual has only one encounter associated with it, removing the identity from the encounter page will not delete the individual if it has social relationships. Users see:
Error: You can't remove this encounter from a marked individual because it is not assigned to one. it is not assigned to one.

The message should instead tell users, "You can't remove this encounter from a marked individual because it has one or more social relationships."

Steps to reproduce:

1. Find or create a Marked Individual with a social relationship (individuals.jsp) with one encounter
2. From the encounter page (encounter.jsp), click the Edit button of the Identity section
3. Under Manage Identity, click the Remove button next to Remove from marked individual
4. "You can't remove this encounter from a marked individual because it is not assigned to one" message appears

Community link

• https://community.wildme.org/t/cannot-delete-encounter/2623
• https://community.wildme.org/t/unable-to-delete-an-encounter-on-whiskerbook/3321
• https://community.wildme.org/t/unable-to-delete-encounters-in-whiskerbook/4375