Disable flutter-candidate-update cron job (#8002)

.github/workflows/flutter-candidate-update.yaml

diff --git a/.github/workflows/flutter-candidate-update.yaml b/.github/workflows/flutter-candidate-update.yaml
index 37de07e..f71e124 100644
--- a/.github/workflows/flutter-candidate-update.yaml
+++ b/.github/workflows/flutter-candidate-update.yaml
@@ -1,9 +1,11 @@
 name: Flutter Candidate Update
 on:
   workflow_dispatch: # Allows for manual triggering if needed
-  schedule:
-    # * is a special character in YAML so you have to quote this string
-    - cron: "0 8/12 * * *" # Run every day at midnight and noon Pacific Time
+  # TODO(https://github.com/flutter/devtools/issues/7939): Re-enable once Flutter candidates
+  # are tagged again.
+  # schedule:
+  #   # * is a special character in YAML so you have to quote this string
+  #   - cron: "0 8/12 * * *" # Run every day at midnight and noon Pacific Time
 
 permissions:
   contents: write