Ignore HF's generation tags in jinja templates

[gakada]

This allows to load e.g. Laguna-XS-2.1, otherwise it will give an error:

jinja2.exceptions.TemplateSyntaxError: Encountered unknown tag 'generation'. Jinja was looking for the following tags: 'elif' or 'else' or 'endif'. The innermost block that needs to be closed is 'if'.

and chat completion won't work.

IgnoreGenerationTags extension is taken from llama-cpp-python.