x/tools/cmd/godoc: remove unused variable

Found with honnef.co/go/tools/cmd/unused.

Change-Id: I3db2aad14de33f0be69569cd355e453173098358
Reviewed-on: https://go-review.googlesource.com/37599
Reviewed-by: Alan Donovan <adonovan@google.com>
diff --git a/cmd/godoc/main.go b/cmd/godoc/main.go
index ec13d1a..227e29b 100644
--- a/cmd/godoc/main.go
+++ b/cmd/godoc/main.go
@@ -53,10 +53,7 @@
 	"golang.org/x/tools/godoc/vfs/zipfs"
 )
 
-const (
-	defaultAddr = ":6060" // default webserver address
-	toolsPath   = "golang.org/x/tools/cmd/"
-)
+const defaultAddr = ":6060" // default webserver address
 
 var (
 	// file system to serve