remove the schedule from the workflow dispatch job (#1683)

Relates to issue #1682. This change removes the schedule to stop the
workflow from failing due to null input values. We can either add this
back with some expressions to set defaults for scheduled runs or create
a simplified build workflow that runs on a schedule.

.github/workflows/build-package-docs.yaml

@@ -2,8 +2,6 @@
 
 name: Ansible package docs build
 on:
-  schedule:
-    - cron: '17 5 * * *'
   workflow_dispatch:
     inputs:
       repository-owner: