Using a pre-built wheel currently requires specifying the right version, e.g. llama-cpp-python==0.3.4

Ran into this problem, and it might be helpful for others if this were clarified in the help text. When I run pip install llama-cpp-python it tries to use 0.3.5, and if that version isn't present in the extra-index-url, it will just ignore it and still try to build the wheel itself.

e.g. for CUDA it reccomends

```
pip install llama-cpp-python \
--extra-index-url https://abetlen.github.io/llama-cpp-python/whl/cu121
```
but it only worked for me after clicking into the link and seeing that it only supports 0.3.4 / 0.2.9 / ...