Upgrade release process to v2 only

[yurishkuro]

• stop publishing v2 docs Remove v1 release logic from documentation release workflow #1042

These probably should be done after actually doing the v2-only release

• remove v1 artifacts from Download page (yaml and template)
• remove all older v1 versions except for the latest v1 (from data/, content/, and hugo.yaml)
• remove content/v1/_dev and make sure it doesn't break the build

[chalin]

I think that we should also clean up the Hugo config. For example, rename:

• fooV2 params to be just foo, such as latestV2; AND ...
• at the same time rename the current bare foo to fooV1

WDYT?

[yurishkuro]

Too much risky work, I don't think it's worth it. At some point we should kill event the remaining v1.76 pages and then such cleanup would make sense.