bytes: fix panic in bytes.Buffer.Peek
This change fixed the overlooked offset in bytes.Buffer.Peek.
Otherwise, it will either return wrong result or panic with
"runtime error: slice bounds out of range".
Change-Id: Ic42fd8a27fb9703c51430f298933b91cf0d45451
GitHub-Last-Rev:
fb97ebc3b188959835706626f66898d6306c16fb
GitHub-Pull-Request: golang/go#76165
Reviewed-on: https://go-review.googlesource.com/c/go/+/717640
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>