cmd/internal/bio: remove unused MustWriter
Change-Id: I70435781fbaeca2b6927a74afd79a3ff123b527b
GitHub-Last-Rev:
cae569f4c4bf73a9a6cd8d26fb080962f94bf1b1
GitHub-Pull-Request: golang/go#71622
Reviewed-on: https://go-review.googlesource.com/c/go/+/647916
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>