fix: Resolving MutualTLSChannelError 'OpenSSL' module error on by adding pyopenssl dependency in pyproject.toml

- Add 'pyopenssl' to project dependencies to fix MutualTLSChannelError  encountered during mTLS channel configuration.

PiperOrigin-RevId: 864874340

Author: google-genai-bot

pyproject.toml

@@ -32,7 +32,7 @@ dependencies = [
   "click>=8.1.8, <9.0.0",                                    # For CLI tools
   "fastapi>=0.124.1, <1.0.0",                                # FastAPI framework
   "google-api-python-client>=2.157.0, <3.0.0",               # Google API client discovery
-  "google-auth>=2.47.0",                                     # Google Auth library
+  "google-auth[pyopenssl]>=2.47.0",                          # Google Auth library
   "google-cloud-aiplatform[agent_engines]>=1.132.0, <2.0.0", # For VertexAI integrations, e.g. example store.
   "google-cloud-bigquery-storage>=2.0.0",
   "google-cloud-bigquery>=2.2.0",