Configure client id and client secret in the config file

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=224158599

javatests/google/registry/config/RegistryConfigTest.java

@@ -25,13 +25,6 @@ import org.junit.runners.JUnit4;
 @RunWith(JUnit4.class)
 public class RegistryConfigTest {
 
-  @Test
-  public void test_clientSecretFilename() {
-    // Verify that we're pulling this from the default.
-    assertThat(RegistryConfig.getClientSecretFilename()).isEqualTo(
-        "/google/registry/tools/resources/client_secret.json");
-  }
-
   @Test
   public void test_reservedTermsExportDisclaimer_isPrependedWithOctothorpes() {
     assertThat(provideReservedTermsExportDisclaimer(CONFIG_SETTINGS.get()))