rollback protobuf to version 3.15

protocolbuffers/protobuf-javascript#105

Author: infynyxx

.github/workflows/ci.yml

@@ -32,7 +32,7 @@ jobs:
     - name: Install Protoc
       uses: arduino/setup-protoc@v2
       with:
-        version: "23.2"
+        version: "3.15"
 
     - name: Print protoc version
       run: protoc --version