Guides was already mostly gone. The two major remaining bits (the "core
workflow" guide and the "recommended practices" guide, which deserves a rename)
make much more sense as highly technical marketing material, and thus have a
natural home in the intro section.
This guide now lives at:
- https://learn.hashicorp.com/terraform#getting-started
...and terraform.io has been redirecting to there for quite a while. This commit
removes the extra copy so that the text of the two versions doesn't drift, and
updates existing links to point to the new location.
Although /intro/getting-started includes docs content, those pages currently
redirect to the Learn platform, and so shouldn't be affected by the large unfurl
image.