acme: remove dead code

The private encodePem() and unique() functions under the acme package
had no call-sites and so can be removed.

Change-Id: Ic617392e7cc9b9e795456626a623ba02df108694
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/676875
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Daniel McCarney <daniel@binaryparadox.net>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

acme/acme.go

@@ -33,7 +33,6 @@ import (
 	"encoding/base64"
 	"encoding/hex"
 	"encoding/json"
-	"encoding/pem"
 	"errors"
 	"fmt"
 	"math/big"
@@ -816,11 +815,5 @@ func tlsChallengeCert(san []string, opt []CertOption) (tls.Certificate, error) {
 	}, nil
 }
 
-// encodePEM returns b encoded as PEM with block of type typ.
-func encodePEM(typ string, b []byte) []byte {
-	pb := &pem.Block{Type: typ, Bytes: b}
-	return pem.EncodeToMemory(pb)
-}
-
 // timeNow is time.Now, except in tests which can mess with it.
 var timeNow = time.Now

acme/autocert/internal/acmetest/ca.go

@@ -782,15 +782,3 @@ func decodePayload(v interface{}, r io.Reader) error {
 func challengeToken(domain, challType string, authzID int) string {
 	return fmt.Sprintf("token-%s-%s-%d", domain, challType, authzID)
 }
-
-func unique(a []string) []string {
-	seen := make(map[string]bool)
-	var res []string
-	for _, s := range a {
-		if s != "" && !seen[s] {
-			seen[s] = true
-			res = append(res, s)
-		}
-	}
-	return res
-}