godoc/proxy: remove unused cacheKey function

Change-Id: Ic7392e973de4a8c9232e9c55ed76c4ca799d68b4
Reviewed-on: https://go-review.googlesource.com/86315
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

godoc/proxy/proxy.go

@@ -10,10 +10,8 @@ package proxy
 
 import (
 	"bytes"
-	"crypto/sha1"
 	"encoding/json"
 	"fmt"
-	"io"
 	"io/ioutil"
 	"net/http"
 	"net/http/httputil"
@@ -121,12 +119,6 @@ func flatten(seq []Event) string {
 	return buf.String()
 }
 
-func cacheKey(body string) string {
-	h := sha1.New()
-	io.WriteString(h, body)
-	return fmt.Sprintf("prog-%x", h.Sum(nil))
-}
-
 func share(w http.ResponseWriter, r *http.Request) {
 	if googleCN(r) {
 		http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)