#141: Edit test data to make sense

- Behaviour of 404s was changed, but the test data wasn't, so it could be confusing why test data saying a 404 should occur then isn't tested that happens (which it shouldn't now)

test/icat/endpoints/test_count_with_filters_icat.py

@@ -38,8 +38,8 @@ def test_valid_no_results_count_with_filters(
         self, flask_test_app_icat, valid_icat_credentials_header,
     ):
         test_response = flask_test_app_icat.get(
-            '/investigations/count?where={"title": {"like": "This filter should cause a'
-            '404 for testing purposes..."}}',
+            '/investigations/count?where={"title": {"like": "This filter should cause 0'
+            ' results to be found for testing purposes..."}}',
             headers=valid_icat_credentials_header,
         )