Fix typo that prevented compiling with Go 1.19

internal/testutil/tlsassertions/assertions_before_go1.20.go

@@ -5,6 +5,6 @@
 
 package tlsassertions
 
-func GetTlsErrorPrefix() string {
+func GetTLSErrorPrefix() string {
 	return ""
 }

internal/testutil/tlsassertions/assertions_test.go

@@ -1,22 +0,0 @@
-// Copyright 2023 the Pinniped contributors. All Rights Reserved.
-// SPDX-License-Identifier: Apache-2.0
-
-package tlsassertions
-
-import (
-	"runtime"
-	"strings"
-	"testing"
-
-	"github.com/stretchr/testify/require"
-)
-
-func TestGetTLSErrorPrefix(t *testing.T) {
-	expected := "tls: failed to verify certificate: "
-
-	if strings.Contains(runtime.Version(), "1.19") {
-		expected = ""
-	}
-
-	require.Equal(t, expected, GetTLSErrorPrefix())
-}