Remove the dependency on non-portable dev-python/cryptography.
https://bugs.gentoo.org/821706#c4 by Alex Xu

--- a/mozilla/certdata2pem.py
+++ b/mozilla/certdata2pem.py
@@ -28,8 +28,6 @@
 import textwrap
 import io

-from cryptography import x509
-

 objects = []

@@ -122,12 +120,6 @@
         if not obj['CKA_LABEL'] in trust or not trust[obj['CKA_LABEL']]:
             continue

-        cert = x509.load_der_x509_certificate(obj['CKA_VALUE'])
-        if cert.not_valid_after < datetime.datetime.now():
-            print('!'*74)
-            print('Trusted but expired certificate found: %s' % obj['CKA_LABEL'])
-            print('!'*74)
-
         bname = obj['CKA_LABEL'][1:-1].replace('/', '_')\
                                       .replace(' ', '_')\
                                       .replace('(', '=')\