fix(conda): pin cryptography 48.0.1 on Intel macOS, which has no newer wheel #1827

Describe the bug
#1825 (merged as 635d8b3cb) builds osx-64 natively on macos-26-intel. cryptography has shipped no Intel macOS wheel since 49.0.0: 48.0.1 has a universal2 wheel, while 49.0.0 and 50.0.2 have none. As a result, that leg builds cryptography==50.0.2 from source and probably links the runner's Homebrew OpenSSL.

Expected behavior
Per the ruling on #1822 (option B), Intel macOS pins cryptography==48.0.1 through a PEP 508 platform marker in conda/requirements.txt, and every other build keeps 50.0.2. util/conda_vendor.py writes that pin and --check accepts it, so Conda Update does not drop it. Tests pin both.

Additional context
This is the follow-up to #1822. #1825 merged before this revision landed.