Removed pull_request trigger and changed concurrency rule

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

@@ -1,9 +1,9 @@
 name: 'Test and Release PyCyphal'
-on: [ push, pull_request ]
+on: push
 
-# Ensures that only one workflow is running at a time - required for duplicate pushes and repushing a PR
+# Ensures that only one workflow is running at a time
 concurrency:
-  group: ${{ github.workflow }}
+  group: ${{ github.workflow_sha }}
   cancel-in-progress: true
 
 jobs:
@@ -30,6 +30,7 @@ jobs:
       - name: Install dependencies
         run: |
           if [ "$RUNNER_OS" == "Linux" ]; then
+            sudo apt-get --ignore-missing update || true
             sudo apt-get install -y linux-*-extra-$(uname -r) graphviz ncat
           fi
           git submodule update --init --recursive