net/rpc: move frozen notice to the start of the package doc
For #71559
Change-Id: I68b9518a26cab75789d596839267abab7997bc2c
Reviewed-on: https://go-review.googlesource.com/c/go/+/646575 Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Rob Pike <r@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Commit-Queue: Ian Lance Taylor <iant@google.com>