all: fix some typos in comment

Change-Id: Ia209f0a6d9b19d14e655c65d1287a1416b48c487
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/707535
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Sean Liao <sean@liao.dev>
Reviewed-by: Nicola Murino <nicola.murino@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sean Liao <sean@liao.dev>

ssh/client_auth_test.go

@@ -1136,7 +1136,7 @@ func TestPickSignatureAlgorithm(t *testing.T) {
 				t.Fatalf("error generating cert signer: %v", err)
 			}
 			// The signer supports the public key algorithm and the
-			// public key format is a certificate type so the cerificate
+			// public key format is a certificate type so the certificate
 			// algorithm matching the key format must be returned
 			_, algo, err = pickSignatureAlgorithm(certSigner, c.extensions)
 			if err != nil {