[skip changelog] Fix publish docs workflow (#1320)

.github/workflows/publish-docs.yaml

@@ -52,12 +52,12 @@ jobs:
       - name: Setup Go
         uses: actions/setup-go@v2
         with:
-          go-version: "1.14"
+          go-version: "1.16"
 
       - name: Install Go dependencies
         run: |
           go version
-          go get -u github.com/pseudomuto/protoc-gen-doc/cmd/protoc-gen-doc
+          go install github.com/pseudomuto/protoc-gen-doc/cmd/protoc-gen-doc@v1.4.1
 
       - name: Install protoc compiler
         uses: arduino/setup-protoc@v1