.github: Bump arduino/setup-protoc from 2 to 3

Bumps [arduino/setup-protoc](https://github.com/arduino/setup-protoc) from 2 to 3.
- [Release notes](https://github.com/arduino/setup-protoc/releases)
- [Commits](arduino/setup-protoc@v2...v3)

---
updated-dependencies:
- dependency-name: arduino/setup-protoc
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/validate-generated-files.yml

@@ -17,7 +17,7 @@ jobs:
           go-version-file: 'go.mod'
 
       - name: Install Protoc
-        uses: arduino/setup-protoc@v2
+        uses: arduino/setup-protoc@v3
 
       - name: Set up Buf
         uses: bufbuild/buf-setup-action@v1