Update library_generation.Dockerfile

Author: blakeli0

.cloudbuild/library_generation/library_generation.Dockerfile

@@ -37,7 +37,7 @@ RUN cp "/root/.m2/repository/com/google/api/gapic-generator-java/${DOCKER_GAPIC_
 FROM docker.io/library/python:3.13.2-slim@sha256:6b3223eb4d93718828223966ad316909c39813dee3ee9395204940500792b740 as final
 
 ARG OWLBOT_CLI_COMMITTISH=3a68a9c0de318784b3aefadcc502a6521b3f1bc5
-ARG PROTOC_VERSION=25.8
+ARG PROTOC_VERSION=32.1
 ARG GRPC_VERSION=1.71.0
 ENV HOME=/home
 ENV OS_ARCHITECTURE="linux-x86_64"