llava : remove prog parameter from ArgumentParser (#5457)

* llava: remove prog parameter from ArgumentParser

This commit removes the `prog` parameter from `ArgumentParser`
so that it uses the default value which is the name of the script.

The motivation for this change is that currently the usage output looks
like this:
```console
$ python examples/llava/convert-image-encoder-to-gguf.py --help
usage: convert_hf_to_gguf.py [-h] ...
```
And with this change it will look like this:
```console
$ python examples/llava/convert-image-encoder-to-gguf.py --help
usage: convert-image-encoder-to-gguf.py [-h] ...
```

Signed-off-by: Daniel Bevenius <daniel.bevenius@gmail.com>

* ci: add W503 to flake8 ignore list

This commit adds W503 to the ignore list for flake8. This is done to
avoid the following error:
W503 line break before binary operator

Signed-off-by: Daniel Bevenius <daniel.bevenius@gmail.com>

---------

Signed-off-by: Daniel Bevenius <daniel.bevenius@gmail.com>