fix: relax protobuf lower bound to restore a2a-sdk compatibility (#285)

Author: jeanscherf

pyproject.toml

@@ -21,8 +21,8 @@ dependencies = [
     "opentelemetry-instrumentation-langchain>=0.61.0",
     "httpx>=0.27.0",
     "PyJWT>=2.13.0",
-    "protobuf>=7.0.0",
-    "protovalidate>=0.13.0",
+    "protobuf>=5.29.5",
+    "protovalidate>=0.14.1",
     "grpcio>=1.60.0",
     "opentelemetry-api>=1.43.0",
     "opentelemetry-sdk>=1.43.0",