Fixes typo in the check_instanceable.py script (#248)

# Description

In line 106 of the `check_instanceable.py` script, there is a typo
error.

The line goes as:

```python
prim_utils.create_prim("/World/envs/env_0/Asset", "Xform", usd_path=os.path.abspath(args_cli.usd_path))
```

but should be:

```python
prim_utils.create_prim("/World/envs/env_0/Asset", "Xform", usd_path=os.path.abspath(args_cli.input))
```

Fixes #242 

## Type of change

- Bug fix (non-breaking change which fixes an issue)

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./orbit.sh --format`
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] I have run all the tests with `./orbit.sh --test` and they pass
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file

Note: These 5 symbols that I changed do not require putting my name on
the contributors list.

source/standalone/tools/check_instanceable.py

@@ -103,7 +103,7 @@ def main():
     prim_utils.create_prim("/World/Light", "DistantLight")
 
     # Everything under the namespace "/World/envs/env_0" will be cloned
-    prim_utils.create_prim("/World/envs/env_0/Asset", "Xform", usd_path=os.path.abspath(args_cli.usd_path))
+    prim_utils.create_prim("/World/envs/env_0/Asset", "Xform", usd_path=os.path.abspath(args_cli.input))
     # Clone the scene
     num_clones = args_cli.num_clones