psl: fix an old unit test that now fails cause it doesn't expect the …

…existence of the new 'prismaSkipIntegrity' relation mode

psl/psl/tests/attributes/relations/referential_actions.rs

@@ -380,7 +380,7 @@ fn foreign_keys_not_allowed_on_mongo() {
     "#};
 
     let expected = expect![[r#"
-        [1;91merror[0m: [1mError validating datasource `relationMode`: Invalid relation mode setting: "foreignKeys". Supported values: "prisma"[0m
+        [1;91merror[0m: [1mError validating datasource `relationMode`: Invalid relation mode setting: "foreignKeys". Supported values: "prisma", "prismaSkipIntegrity"[0m
           -->  schema.prisma:3
            | 
          2 |   provider = "mongodb"