test: Fix r-string test (#4637)

Author: max-sixty

prqlc/prqlc-parser/src/test.rs

@@ -1824,7 +1824,7 @@ fn test_dates() {
 #[test]
 fn test_multiline_string() {
     assert_yaml_snapshot!(parse_single(r##"
-        derive x = r#"r-string test"#
+        derive x = r"r-string test"
         "##).unwrap(), @r###"
     ---
     - VarDef:
@@ -1835,9 +1835,10 @@ fn test_multiline_string() {
             name:
               Ident: derive
             args:
-              - Ident: r
+              - Literal:
+                  String: r-string test
                 alias: x
-      span: "0:9-39"
+      span: "0:9-37"
     "### )
 }