generator: rename template variable

[ErikSchierboom]

This is done in preparation of changing the order of the generator calls, as we want to keep the :description from the canonical data and not overwrite it. I'm open to naming suggestions.

[tasxatzial]

So, what's the plan here? Could you give a brief explanation so I have some context? :)

[ErikSchierboom]

Well, previously we overwrote the description property with the value used in the templates that contains the test case's description. As suggested previously, the description property should be set before the callbacks in the generator.clj are called, as that will allow you to update the description in those callbacks. But as some exercises use the description, we can't overwrite its value before that is called.

[tasxatzial]

Thanks. I think 'context' is fine, not going to be too picky about naming at this point. If anything comes up, we can update later.