docs for `vars` property in task step confusing and repetitive

[Kris De Volder]

Two points.

1. A section of the 'vars' doc section seems to be repeated (some kind of copy-pasting error maybe?).

See: https://concourse-ci.org/task-step.html#task-step-vars

See the code snippet:

plan:
- get: my-repo
- task: integration
  file: my-repo/ci/task.yml
  vars:
    text: "Hello World!"

It is repeated twice. Was the second snippet meant to be something else? Or was it just accidentally pasted twice?

2. I don't think I quite understand the difference between 'vars' and 'params'. There's some explanation in the docs but it still leaves me scratching my head a bit. The main difference is that 'vars' supports interpolation? Not sure what exactly that means in concrete terms (i.e. what exactly is it that we can do with 'vars' but not 'params'.

PS: About point 2), I'm sorry I know this is a bit of a vague complaint. If it seems too hard to improve this without making it incredibly verbose, I understand, but I thought I'd at least report it and give you guys a chance to take another look and decide. I figure you might as well, while you are already looking at it to take care of point 1)

[Alex Suraci]

Thanks for the feedback. :) vars vs. params is definitely prone to confusion, I'll take a look