fix: do not split main.py on 'def main' (#5895)

doesn't work well in edge cases:

```
@schedule(
    bla=True
)
def main(x: str):
    return x
```

```
error_message = """
Please ensure you have defined main(username, password) correctly.
The function def main( should be at the end.
"""

def main(x: str):
    return x
```

Co-authored-by: Ruben Fiszel <ruben@windmill.dev>

backend/parsers/windmill-parser-py-imports/src/lib.rs

@@ -391,7 +391,7 @@ async fn parse_python_imports_inner(
                 })
                 .join("\n")
                 .parse::<toml::Table>()
-            .map_err(to_anyhow)?;
+                .map_err(to_anyhow)?;
 
             {
                 if let Some(v) = metadata.get("requires-python").and_then(|v| v.as_str()) {