cmd/go: fix mod_get_fallback test

Fixes #43795

Change-Id: I3d791d0ac9ce0b523c78c649aaf5e339a7f63b76
Reviewed-on: https://go-review.googlesource.com/c/go/+/284797
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

Author: Jay Conrod

src/cmd/go/testdata/script/mod_get_fallback.txt

@@ -6,5 +6,5 @@ env GOPROXY=https://proxy.golang.org,direct
 env GOSUMDB=off
 
 go get -x -v -d golang.org/x/tools/cmd/goimports
-stderr '# get https://proxy.golang.org/golang.org/x/tools/@latest'
+stderr '# get https://proxy.golang.org/golang.org/x/tools/@v/list'
 ! stderr '# get https://golang.org'