Update nanopb download URL in workflow

.github/workflows/update_protobufs.yml

@@ -27,7 +27,7 @@ jobs:
 
       - name: Download nanopb
         run: |
-          wget https://jpa.kapsi.fi/nanopb/download/nanopb-0.4.9.1-linux-x86.tar.gz
+          wget https://github.com/nanopb/nanopb/releases/download/nanopb-0.4.9.1/nanopb-0.4.9.1-linux-x86.tar.gz
           tar xvzf nanopb-0.4.9.1-linux-x86.tar.gz
           mv nanopb-0.4.9.1-linux-x86 nanopb-0.4.9