fix: add cyrptography package to prerelease tests

Author: parthea

gapic/templates/noxfile.py.j2

@@ -502,6 +502,7 @@ def prerelease_deps(session, protobuf_implementation):
         "grpcio-status",
         "protobuf",
         "proto-plus",
+        "cryptography",  # required by google-auth v3.x
     ]
 
     for dep in prerel_deps:
@@ -602,6 +603,9 @@ def core_deps_from_source(session, protobuf_implementation):
         session.install(dep, "--no-deps", "--ignore-installed")
         print(f"Installed {dep}")
 
+    # Required by google-auth v3.x
+    session.install(cryptography)
+
     session.run(
         "py.test",
         "tests/unit",