Update varnish.rst

[Dreimus]

remove word in vcl_recv doesnt exist in varnish 4.*

[xabbuh]

@dbu Can you confirm this change?

[dbu]

seems correct: https://www.varnish-cache.org/docs/4.0/whats-new/upgrading.html#the-remove-keyword-is-gone

this fix should be applied to the oldest maintained version of the docs, its probably wrong in all branches.

[wouterj]

Hi @Dreimus! Thank you for fixing this example.

As we restructured the documentation recently, this PR couldn't be merged as is. I've rebased your commit against the new changes and created #6848. You're still the author of the commit, so you get all credits you deserve.

Thanks again and I hope to see you back with more nice PRs! :)