Replace deprecated CharMatcher method

CharMatcher.isLetterOrDigit() is deprecated for failing to support
supplementary characters. We explicitly declare a matcher for ascii
letters and digits.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=252671830

javatests/google/registry/util/RegistrarUtilsTest.java

@@ -0,0 +1,36 @@
+// Copyright 2019 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.util;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link RegistrarUtils}. */
+@RunWith(JUnit4.class)
+public class RegistrarUtilsTest {
+
+  @Test
+  public void testNormalizeRegistrarName_letterOrDigitOnly() {
+    assertThat(RegistrarUtils.normalizeRegistrarName("129abzAZ")).isEqualTo("129abzaz");
+  }
+
+  @Test
+  public void testNormalizeRegistrarName_hasSymbols() {
+    assertThat(RegistrarUtils.normalizeRegistrarName("^}129a(bzAZ/:")).isEqualTo("129abzaz");
+  }
+}