[http-client-python] pyproject.toml - keep non-generated project.urls

If project.urls are manually added in, they should be kept.

I believe the changes should be:
- adding pyproject.urls to [the KEEP_FIELDS](https://github.com/microsoft/typespec/blob/0e1bc513a515ee9f4966d043c114887442c9d39f/packages/http-client-python/generator/pygen/codegen/serializers/general_serializer.py#L76)
- updating the urls in the pyproject.toml template with the KEEP_FIELDS: https://github.com/microsoft/typespec/blob/0e1bc513a515ee9f4966d043c114887442c9d39f/packages/http-client-python/generator/pygen/codegen/templates/packaging_templates/pyproject.toml.jinja2#L80