integration: Remove test_create_check_duplicate

[akerouanton]

moby/moby#46251 marks CheckDuplicate as deprecated. Any NetworkCreate request with a conflicting network name will now return an error.

[akerouanton]

@milas PTAL 🤗

[thaJeztah]

AttachContainerTest.test_attach_no_stream ___________________
tests/integration/api_container_test.py:1299: in test_attach_no_stream
    assert output == 'hello\n'.encode(encoding='ascii')
E   AssertionError: assert b'' == b'hello\n'
E     Use -v to get more diff
___________________ TestNetworks.test_create_check_duplicate ___________________
tests/integration/api_network_test.py:330: in test_create_check_duplicate
    self.tmp_networks.append(net_id['Id'])
E   TypeError: string indices must be integers

Ha! Wondering if the last failure is an implicit type conversion; if the network ID could be parsed as a hexadecimal🤔

Let me try restarting CI

[thaJeztah]

Although it failed in 2 check, so perhaps that line needs to be removed (and was only needed for the second test?)

[thaJeztah]

LGTM

@milas PTAL