Turn off template feature of project repo

[bielsnohr]

Once #249 is closed, the project repo at carpentries-incubator/python-intermediate-inflammation should be made into a normal repo, turning off the "Template repository" feature. This will ensure that learners can only fork and not use the template.

Under general settings, the option is a simple toggle:

[anenadic]

Hold off from turning the template feature for now as it will break people's forks of the material. Once we notify them all of this change and give them sufficient time to switch to the latest version of the material - we will turn the template off.