Check for TUF expirations 2x daily, and warn 4 days in advance rather than 2 (#23039)

.github/workflows/check-tuf-timestamps.yml

@@ -6,7 +6,7 @@ on:
       - '.github/workflows/check-tuf-timestamps.yml'
   workflow_dispatch: # Manual
   schedule:
-    - cron: '0 10 * * *'
+    - cron: '0 10,22 * * *'
 
 # This allows a subsequently queued workflow run to interrupt previous runs
 concurrency:
@@ -38,7 +38,7 @@ jobs:
       run: |
         expires=$(curl -s http://tuf.fleetctl.com/timestamp.json | jq -r '.signed.expires' | cut -c 1-10)
         today=$(date "+%Y-%m-%d")
-        warning_at=$(date -d "$today + 2 day" "+%Y-%m-%d")
+        warning_at=$(date -d "$today + 4 day" "+%Y-%m-%d")
         expires_sec=$(date -d "$expires" "+%s")
         warning_at_sec=$(date -d "$warning_at" "+%s")