Bump protobuf from 4.25.5 to 4.25.6

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 4.25.5 to 4.25.6.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/protobuf_release.bzl)
- [Commits](protocolbuffers/protobuf@v4.25.5...v4.25.6)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements-dev.txt

@@ -531,7 +531,7 @@ proto-plus==1.23.0
     #   -r requirements-tests.txt
     #   google-api-core
     #   google-cloud-private-ca
-protobuf==4.25.5
+protobuf==4.25.6
     # via
     #   -r requirements-tests.txt
     #   google-api-core

requirements-docs.txt

@@ -549,7 +549,7 @@ proto-plus==1.23.0
     #   -r requirements-tests.txt
     #   google-api-core
     #   google-cloud-private-ca
-protobuf==4.25.5
+protobuf==4.25.6
     # via
     #   -r requirements-tests.txt
     #   google-api-core

requirements-tests.txt

@@ -431,7 +431,7 @@ proto-plus==1.23.0
     #   -r requirements.txt
     #   google-api-core
     #   google-cloud-private-ca
-protobuf==4.25.5
+protobuf==4.25.6
     # via
     #   -r requirements.txt
     #   google-api-core

requirements.txt

@@ -235,7 +235,7 @@ proto-plus==1.23.0
     # via
     #   google-api-core
     #   google-cloud-private-ca
-protobuf==4.25.5
+protobuf==4.25.6
     # via
     #   -r requirements.in
     #   google-api-core