all: revert "all: prefer strings.LastIndexByte over strings.LastIndex"

This reverts https://golang.org/cl/66372.

Updates #22148

Change-Id: I3e94af3dfc11a2883bf28e1d5e1f32f98760b3ee
Reviewed-on: https://go-review.googlesource.com/68431
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/vet/print.go

diff --git a/src/cmd/vet/print.go b/src/cmd/vet/print.go
index 453a072..21bb0d0 100644
--- a/src/cmd/vet/print.go
+++ b/src/cmd/vet/print.go
@@ -38,7 +38,7 @@
 
 		// Backwards compatibility: skip optional first argument
 		// index after the colon.
-		if colon := strings.LastIndexByte(name, ':'); colon > 0 {
+		if colon := strings.LastIndex(name, ":"); colon > 0 {
 			name = name[:colon]
 		}