tests: Remove manual delete of the TAP interface in test_tap_from_fd

By using `net_util::open_tap` to create the TAP interface, the created
interface will be deleted when the returned variable (`net_utils::Tap`)
is dropped.

Signed-off-by: Bo Chen <chen.bo@intel.com>

tests/integration.rs

@@ -5724,11 +5724,6 @@ mod tests {
             let _ = child.kill();
             let output = child.wait_with_output().unwrap();
 
-            std::process::Command::new("bash")
-                .args(&["-c", "sudo ip tuntap del mode tap name chtap0"])
-                .status()
-                .expect("Expected upping interface to work");
-
             handle_child_output(r, &output);
         }
     }