Add skipif mark to test_code_v1 in github CI

[Copilot]

The test_code_v1 test was marked xfail on GitHub CI due to 2FA-related SSH failures on the Mila cluster. Since the test cannot run in that environment at all, skipif is more appropriate than xfail.

Changes

• tests/integration/test_code_v1.py: Replace @pytest.mark.xfail(in_github_CI, raises=SSHConnectionError, ...) with @pytest.mark.skipif(in_github_CI, ...) — test is now skipped outright in GitHub CI rather than run and expected to fail
• Remove the now-unused SSHConnectionError import

# Before
@pytest.mark.xfail(
    in_github_CI,
    raises=SSHConnectionError,
    reason="Misbehaving since the 2FA changes on the Mila cluster.",
)

# After
@pytest.mark.skipif(
    in_github_CI,
    reason="Misbehaving since the 2FA changes on the Mila cluster.",
)

Original prompt

use a skip mark instead of xfail (see the last commit for context)

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