fix: fix non-existing saml cert test

Author: nijel

test-saml

@@ -2,5 +2,5 @@
 if [ "$1" = "saml" ] ; then
   docker compose exec -T weblate openssl x509 -in /app/data/ssl/saml.crt -text -noout
 else
-  docker compose exec -T weblate test -not -f /app/data/ssl/saml.crt
+  docker compose exec -T weblate test ! -f /app/data/ssl/saml.crt
 fi