test: Increase the CI schedule frequency again

.github/workflows/ci-reliability-test.yml

@@ -1,15 +1,15 @@
 name: new-ci-test
 on:
   schedule:
-    - cron: "*/20 * * * *"
+    - cron: "*/15 * * * *"
   push:
     branches: [chain_agnostic_tests]
   workflow_dispatch:
 
 jobs:
   integration:
     runs-on: pierre-l
-    timeout-minutes: 20
+    timeout-minutes: 15
     steps:
       - uses: actions/checkout@v3
       - uses: dtolnay/rust-toolchain@stable