all: remove redundant type conversion

Change-Id: I4de1d39f8b72cd1116c56fb00b224a60de035f9e
GitHub-Last-Rev: 4e40ee8059695468e62ba9213058b5cc1e4a8e0a
GitHub-Pull-Request: golang/oauth2#586
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/428982
Reviewed-by: Cody Oss <codyoss@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

jws/jws.go

@@ -178,5 +178,5 @@ func Verify(token string, key *rsa.PublicKey) error {
 
 	h := sha256.New()
 	h.Write([]byte(signedContent))
-	return rsa.VerifyPKCS1v15(key, crypto.SHA256, h.Sum(nil), []byte(signatureString))
+	return rsa.VerifyPKCS1v15(key, crypto.SHA256, h.Sum(nil), signatureString)
 }