index/suffixarray: use built-in clear to simplify code
"sais2.go" is regenerated by the command "go generate ./...".
Change-Id: I4307e9fa1f20ea59e3a0d4841dbb22e9cffefa5a
GitHub-Last-Rev:
d285183e654fe412a3470e475fa1ea29e5973b78
GitHub-Pull-Request: golang/go#66376
Reviewed-on: https://go-review.googlesource.com/c/go/+/572198
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Commit-Queue: Ian Lance Taylor <iant@golang.org>