cmd/go/internal/lockedfile/internal/filelock: remove unused type token

Change-Id: If815d17851e4e4eac026417b820f15d11939d9cc
Reviewed-on: https://go-review.googlesource.com/c/go/+/436595
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

src/cmd/go/internal/lockedfile/internal/filelock/filelock_fcntl.go

@@ -39,8 +39,6 @@ type inodeLock struct {
 	queue []<-chan File
 }
 
-type token struct{}
-
 var (
 	mu     sync.Mutex
 	inodes = map[File]inode{}