Upgrade protobuf to 6.x for nvidia-riva-client 2.25.1 compatibility

nvidia-riva-client 2.25.1 ships with gencode compiled against protobuf
6.31.1, which requires a runtime >= 6.31.1. Update protobuf from 5.29.6
to >=6.31.1,<7 and grpcio-tools from 1.67.1 to 1.78.0 to match.
Regenerate frames_pb2.py with the new compiler.

src/pipecat/frames/protobufs/frames_pb2.py

@@ -2,7 +2,7 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
 # NO CHECKED-IN PROTOBUF GENCODE
 # source: frames.proto
-# Protobuf Python Version: 5.27.2
+# Protobuf Python Version: 6.31.1
 """Generated protocol buffer code."""
 from google.protobuf import descriptor as _descriptor
 from google.protobuf import descriptor_pool as _descriptor_pool
@@ -11,9 +11,9 @@ from google.protobuf import symbol_database as _symbol_database
 from google.protobuf.internal import builder as _builder
 _runtime_version.ValidateProtobufRuntimeVersion(
     _runtime_version.Domain.PUBLIC,
-    5,
-    27,
-    2,
+    6,
+    31,
+    1,
     '',
     'frames.proto'
 )