Cleanup and grooming of CI (#205)

(cherry picked from commit 4643983)

Author: christophfroehlich

.github/workflows/humble-build.yml

@@ -12,7 +12,7 @@ on:
       - humble
   schedule:
     # Run every morning to detect flakiness and broken dependencies
-    - cron: '28 6 * * *'
+    - cron: '28 6 * * MON-FRI'
 
 concurrency:
   # cancel previous runs of the same workflow, except for pushes on master branch

.github/workflows/jazzy-build.yml

@@ -12,7 +12,7 @@ on:
       - jazzy
   schedule:
     # Run every morning to detect flakiness and broken dependencies
-    - cron: '28 6 * * *'
+    - cron: '28 6 * * MON-FRI'
 
 concurrency:
   # cancel previous runs of the same workflow, except for pushes on jazzy branch

.github/workflows/prerelease.yaml

@@ -12,7 +12,7 @@ on:
       - master
   schedule:
     # Run every morning to detect flakiness and broken dependencies
-    - cron: '28 6 * * *'
+    - cron: '28 6 * * MON-FRI'
 
 concurrency:
   # cancel previous runs of the same workflow, except for pushes on master branch