fix: ignores pitr backup tests

This feature is not yet finished in the backend. We should re-enable
once this is completed.

google-cloud-spanner/src/test/java/com/google/cloud/spanner/it/ITPitrBackupTest.java

@@ -34,12 +34,15 @@
 import java.util.concurrent.TimeUnit;
 import org.junit.BeforeClass;
 import org.junit.ClassRule;
+import org.junit.Ignore;
 import org.junit.Test;
 import org.junit.experimental.categories.Category;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 import org.threeten.bp.Duration;
 
+// TODO: Enable this test once the backup functionality is supported.
+@Ignore("PITR backups are not yet supported through the client library")
 @Category(ParallelIntegrationTest.class)
 @RunWith(JUnit4.class)
 public class ITPitrBackupTest {