doc: fix grammar and spelling
Minor typo fixes in the docs
Change-Id: I56b5d0318936aecc7775fb5bc70534456707da49
GitHub-Last-Rev:
b4d042f8a997aa0d3824d8f9350dd24090b21073
GitHub-Pull-Request: golang/go#73531
Reviewed-on: https://go-review.googlesource.com/c/go/+/668815
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>