fix: add cryptography to constraints file

[parthea]

This PR is needed to address the following failure in the core_deps_from_source-3.14 presubmit in google-cloud-python here. See the stack trace below

==================================== ERRORS ====================================
____________ ERROR collecting tests/unit/gapic/test_client_info.py _____________
ImportError while importing test module '/home/runner/work/google-cloud-python/google-cloud-python/packages/google-api-core/tests/unit/gapic/test_client_info.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/opt/hostedtoolcache/Python/3.14.2/x64/lib/python3.14/importlib/__init__.py:88: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
tests/unit/gapic/test_client_info.py:23: in <module>
    from google.api_core.gapic_v1 import client_info
google/api_core/gapic_v1/__init__.py:18: in <module>
    from google.api_core.gapic_v1 import method
google/api_core/gapic_v1/method.py:24: in <module>
    from google.api_core import grpc_helpers
google/api_core/grpc_helpers.py:23: in <module>
    import google.auth.transport.grpc
.nox/core_deps_from_source-protobuf_implementation-python/lib/python3.14/site-packages/google/auth/transport/grpc.py:23: in <module>
    from google.oauth2 import service_account
.nox/core_deps_from_source-protobuf_implementation-python/lib/python3.14/site-packages/google/oauth2/service_account.py:78: in <module>
    from google.auth import _service_account_info
.nox/core_deps_from_source-protobuf_implementation-python/lib/python3.14/site-packages/google/auth/_service_account_info.py:20: in <module>
    from google.auth import crypt
.nox/core_deps_from_source-protobuf_implementation-python/lib/python3.14/site-packages/google/auth/crypt/__init__.py:41: in <module>
    from google.auth.crypt import es
.nox/core_deps_from_source-protobuf_implementation-python/lib/python3.14/site-packages/google/auth/crypt/es.py:21: in <module>
    import cryptography.exceptions

Dependencies are installed with the --no-deps option during this pre-release test in order to ensure that pre-release versions of dependencies are not downgraded to the stable versions. In this case, we want to ensure that pre-release versions are used for the purpose of having a comprehensive pre-release test. This means that when a new dependency is added to a core dependency, we need to manually add it to the constraints file which is used during the pre-release test.

gapic-generator-python/gapic/templates/noxfile.py.j2

Lines 601 to 603 in 1919b50

	for dep in core_dependencies_from_source:
	session.install(dep, "--no-deps", "--ignore-installed")
	print(f"Installed {dep}")

gapic-generator-python/gapic/templates/noxfile.py.j2

Lines 566 to 573 in 1919b50

	# Because we test minimum dependency versions on the minimum Python
	# version, the first version we test with in the unit tests sessions has a
	# constraints file containing all dependencies and extras.
	with open(
	CURRENT_DIRECTORY / "testing" / f"constraints-{ALL_PYTHON[0]}.txt",
	encoding="utf-8",
	) as constraints_file:
	constraints_text = constraints_file.read()