python3-cryptography: Cleanup DEPENDS/RDEPENDS

python3-cryptography: Cleanup DEPENDS/RDEPENDS

idna was removed in 3.1, asn1crypto in 2.8, six in 3.3.1; setuptools
never appears to have been a runtime requirement. With these removed the
recipe both builds and passes ptest:

  ===== 2824 passed, 52 skipped, 85319 subtests passed in 3932.89s (1:05:32) =====

Also drop redundant ${PYTHON_PN}-setuptools-rust-native DEPENDS as this
comes from python_setuptools3_rust.bbclass.

Signed-off-by: Alex Kiernan <alexk@zuma.ai>
Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>