Fix Python codegen for enums (#6746)

### What

The way enum types were codegen'd in Python was incompatible with python
<=3.9. This PR fixes this.

### Checklist
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* Using examples from latest `main` build:
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* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/6746?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
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- [PR Build Summary](https://build.rerun.io/pr/6746)
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crates/re_types_builder/src/codegen/python/mod.rs

@@ -871,11 +871,13 @@ fn code_for_enum(
         }
     }
 
-    let variants = obj
-        .fields
-        .iter()
-        .map(|v| format!("Literal[{:?}]", v.pascal_case_name().to_lowercase()))
-        .join(" | ");
+    let variants = format!(
+        "Literal[{}]",
+        obj.fields
+            .iter()
+            .map(|v| format!("{:?}", v.pascal_case_name().to_lowercase()))
+            .join(", ")
+    );
     code.push_unindented(format!("{name}Like = Union[{name}, {variants}]"), 1);
     code.push_unindented(
         format!(