Update README.md

[mehryar]

Fixing typo in install instructions.
I'm sure there is a 0.19.2 version in the works but this PR is to prevent people from wasting time troubleshooting why these install instructions aren't working - since there is no 0.19.2 release on GitHub yet.

[github-actions]

Thanks for suggesting these code changes. To set expectations:

• Pull requests are reviewed in batches, so it can take some time to get a response.
• Smaller pull requests are easier to review. To fix nine typos, nine specific issues will always go faster than one big one. Learn why here.
• Reviewers may not know as much as you about certain situations, so add links to supporting evidence for important claims, especially regarding standards for CSS, HTTP, URI, etc.

Finally, please be patient with the core team. They are trying their best with limited resources.

[evancz]

This PR came in right as 0.19.2 was in pre-release, so the information should be correct now.

I think the root is that the links on various websites point to the "latest" version of the file, so this is a consequence of bringing code into the main branch before the final public release.