TLA CI validation fix: Call `apt update` (#5277)

.azure-pipelines-templates/trace_validation.yml

@@ -1,5 +1,7 @@
 steps:
   - script: |
+      set -ex
+      sudo apt update
       sudo apt install -y default-jre
       python3 ./tla/install_deps.py
     displayName: "Install TLA dependencies"