python3-cryptography: enforce identical version for -cryptography-vectors

python3-cryptography: enforce identical version for -cryptography-vectors

python3-cryptography and python3-cryptography-vectors are actually the
same project but are on Pypi as two separate modules.

The test suite validates that they're the same version and fails if they
are not:

FAIL: tests/test_utils.py::test_vector_version
    def test_vector_version():
>       assert cryptography.__version__ == cryptography_vectors.__version__
E       AssertionError: assert '36.0.2' == '36.0.1'

Catch this slightly earlier by mandating that python3-cryptography-ptest
pulls in an identically versioned python3-cryptography-vectors.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>