Remove proxy_read_timeout and proxy_connect_timeout settings from runners-cache-5

In our current configuration of runners cache server we have following settings of Nginx proxy:

proxy_read_timeout 3600;
proxy_connect_timeout 300;

It seems that settings were added with a misunderstanding what they are for: proxy_read_timeout, proxy_connect_timeout. Having 1 hour of timeout between two subsequent read operations or 5 minutes timeout for establishing connection between Nginx and Minio is not what we want and - with other configuration parameters that were improved recently - it's probably one of many causes of our recent cache server outages.

The above settings were manually commented on runners-cache-5.gitlab.com. After adding the change we've noticed a little improvement. Now we should remove these settings from gitlab-docker cookbook and make the change persistent.