LP#1694529: tweak wording of collision alert message

LP#1694529: tweak wording of collision alert message

And here's a test plan for the patch series as a whole:

[1] In the web staff client, retrieve a patron that has some
    loans. In a separate window, open the patron editor
    for that same patron.
[2] In the first window, mark one of the patron's loans
    as either claims returned or claims never checked out.
[3] In the second window, make a change and attempt to save
    the record. You should see a alert dialog saying that
    the record could not be saved.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>