Update libsnmp dependency for newer ubuntu

It seems the upstream `ubuntu-latest` action runner was updated by
GitHub 4 days ago. The latest ubuntu is now 22.04, which features
libsnmp40 rather than libsnmp35.

.github/workflows/build-and-test.yml

@@ -64,7 +64,7 @@ jobs:
       - name: "Install libraries needed to build external dependencies"
         run: |
           set -xe
-          sudo apt-get install -y libldap2-dev libsasl2-dev libtidy5deb1 libsnmp35
+          sudo apt-get install -y libldap2-dev libsasl2-dev libtidy5deb1 libsnmp40
 
       - uses: browser-actions/setup-chrome@latest
       - run: chrome --version