Add `typeguard` to `requirements.txt`

Before this we got `RuntimeError`:

```bash
Exit code: 1. Reason: Traceback (most recent call last):
File "/home/user/app/app.py", line 6, in <module>
from transformer_lens import HookedTransformer
File "/usr/local/lib/python3.10/site-packages/transformer_lens/__init__.py", line 13, in <module>
from .SVDInterpreter import SVDInterpreter
File "/usr/local/lib/python3.10/site-packages/transformer_lens/SVDInterpreter.py", line 10, in <module>
from typeguard import typechecked
ModuleNotFoundError: No module named 'typeguard'
```

when running the app.

Not sure why this started happening. The app probably was not restarted for about a year so
I imagine the environment on HuggingFace might have changed a bit or some other dependencies...

Fingers crossed that this fixes the issue 😇💆‍♂️

requirements.txt

@@ -2,3 +2,4 @@ gradio==4.31.5
 pytest==8.2.1
 spaces==0.28.3
 transformer-lens==1.15.0
+typeguard==4.4.4