CI: install protobuf-compiler for Rust volume server builds

The prost-build crate requires protoc to compile .proto files.

.github/workflows/rust-volume-server-tests.yml

@@ -34,6 +34,9 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v6
 
+      - name: Install protobuf compiler
+        run: sudo apt-get update && sudo apt-get install -y protobuf-compiler
+
       - name: Install Rust toolchain
         uses: dtolnay/rust-toolchain@stable
 
@@ -68,6 +71,9 @@ jobs:
         with:
           go-version: ${{ env.GO_VERSION }}
 
+      - name: Install protobuf compiler
+        run: sudo apt-get update && sudo apt-get install -y protobuf-compiler
+
       - name: Install Rust toolchain
         uses: dtolnay/rust-toolchain@stable