[yugabyte#5122] Fix TestDeleteEmptyTable

Summary:
After Disabling the 'ignore deleted tables' feature in the D9297 hotfix, it broke
TestDeleteEmptyTable.  This is a false positive.  The error message slightly changes based on
whether the table information is brought into RAM on load or not but it is functionally equivalent.
Fixed the unit test to be less detailed on error message expectations.

Test Plan: TestDeleteEmptyTable

Reviewers: rao, bogdan, alex

Reviewed By: alex

Subscribers: ybase

Differential Revision: https://phabricator.dev.yugabyte.com/D9306

Author: nspiegelberg

src/yb/integration-tests/delete_table-test.cc

@@ -335,8 +335,7 @@ TEST_F(DeleteTableTest, TestDeleteEmptyTable) {
     ASSERT_OK(cluster_->master_proxy()->GetTabletLocations(req, &resp, &rpc));
     SCOPED_TRACE(resp.DebugString());
     ASSERT_EQ(1, resp.errors_size());
-    ASSERT_STR_CONTAINS(resp.errors(0).ShortDebugString(),
-                        "code: NOT_FOUND message: \"Unknown tablet");
+    ASSERT_STR_CONTAINS(resp.errors(0).ShortDebugString(), "code: NOT_FOUND");
   }
 
   // 4) The master 'dump-entities' page should not list the deleted table or tablets.