test-network: suppress too much outputs of state file

Follow-up for 0f9efffaeb.

test/test-network/systemd-networkd-tests.py

@@ -5126,7 +5126,6 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         # Let's wait for the expected DNS server being listed in the state file.
         for _ in range(100):
             output = read_link_state_file('veth99')
-            print(output)
             if 'DNS=2600::ee' in output:
                 break
             time.sleep(.2)