Disable nightly CI temporarily (#18820)

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

Author: ydshieh

.github/workflows/self-nightly-scheduled.yml

@@ -8,8 +8,9 @@ name: Self-hosted runner (nightly)
 
 on:
  repository_dispatch:
- schedule:
- - cron: "0 16 * * *"
+# Disable temporarily until the test suite can be run under 12 hours.
+# schedule:
+# - cron: "0 16 * * *"
 
 env:
  HF_HOME: /mnt/cache