ci: drop nightly cron schedules in HealthChat fork

The schedule triggers on build-and-test.yaml and build_desktop_and_deploy.yaml
fired nightly from the default branch (release/healthchat) and failed at startup,
since the repo gate only skips jobs, not the cron-spawned runs. Remove the
schedule triggers; pull_request/merge_group/push/release/workflow_dispatch are
untouched.

.github/workflows/build-and-test.yaml

@@ -9,9 +9,6 @@
 # Produces multiple Playwright report artifacts
 name: Build & Test
 on:
-    # CRON to run all Projects at 6am UTC
-    schedule:
-        - cron: "0 6 * * *"
     pull_request: {}
     merge_group:
         types: [checks_requested]