test: Add missing test table cleanup for MaterializedViewIT (#2721)

Change-Id: I1281568894ac2d04f0aafe0aa7f4efa7570ae58a

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Fixes #<issue_number_goes_here> ☕️

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Author: trollyxia

google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/admin/v2/it/BigtableMaterializedViewIT.java

@@ -36,6 +36,7 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.logging.Logger;
+import org.junit.After;
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.ClassRule;
@@ -46,6 +47,7 @@
 
 @RunWith(JUnit4.class)
 public class BigtableMaterializedViewIT {
+
   @ClassRule public static final TestEnvRule testEnvRule = new TestEnvRule();
   @Rule public final PrefixGenerator prefixGenerator = new PrefixGenerator();
   private static final Logger LOGGER = Logger.getLogger(BigtableMaterializedViewIT.class.getName());
@@ -71,6 +73,13 @@ public void setUp() throws InterruptedException, IOException {
     testTable = createTestTable(testEnvRule.env().getTableAdminClient());
   }
 
+  @After
+  public void tearDown() throws InterruptedException {
+    if (testTable != null) {
+      testEnvRule.env().getTableAdminClient().deleteTable(testTable.getId());
+    }
+  }
+
   @Test
   public void createMaterializedViewAndGetMaterializedViewTest() {
     String materializedViewId = prefixGenerator.newPrefix();