README.md: Remove some unnecessary material
README.md: Remove some unnecessary material

- The docs are now available online.
- Remove reference to a module that probably shouldn't be used.

Change-Id: If926692eeb7db7100b77d3e9e1b0b9030e593d78
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/34040
Pigweed-Auto-Submit: Wyatt Hepler <cca3bedb37979eacd157a9bceb473582df8aea1e@google.com>
Commit-Queue: Auto-Submit <14637eda5603879df170705285bf30f5996692f0@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: David Rogers <82b08570d73cda922b440ccc756abc5b3ef4c372@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed