increase TUF expiration warning by one day

hopefully this will get obsolete before we have time to use it, but just
in case this increments the warning time to give us more leeway.

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

@@ -38,11 +38,11 @@ jobs:
       run: |
         expires=$(curl -s http://tuf.fleetctl.com/timestamp.json | jq -r '.signed.expires' | cut -c 1-10)
         today=$(date "+%Y-%m-%d")
-        tomorrow=$(date -d "$today + 1 day" "+%Y-%m-%d")
+        warning_at=$(date -d "$today + 2 day" "+%Y-%m-%d")
         expires_sec=$(date -d "$expires" "+%s")
-        tomorrow_sec=$(date -d "$tomorrow" "+%s")
+        warning_at_sec=$(date -d "$warning_at" "+%s")
         
-        if [ "$expires_sec" -le "$tomorrow_sec" ]; then
+        if [ "$expires_sec" -le "$warning_at_sec" ]; then
             exit 1
         else
             exit 0