Increase uwsgi_buffer_size for nginx config

[edsu]

Description

I was playing back a YouTube video and noticed that the playback worked
fine with using uwsgi/pywb directly but failed when using nginx. I think
a very long HTTP Link header was causing nginx to hang up. I increased
the uwsgi_buffer_size to 8k and the problem went away. Maybe this will
save someone else some time if it is increased?

Motivation and Context

https://nginx.org/en/docs/http/ngx_http_uwsgi_module.html#uwsgi_buffer_size

Types of changes

• Replay fix (fixes a replay specific issue)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added or updated tests to cover my changes.
• All new and existing tests passed.