ci: rename workflow 'Docker Images For Repo Handling' -> 'Docker Images For Automation'

The previous display name was historical and no longer described what
the workflow actually does. 'Docker Images For Automation' matches its
real purpose — building / refreshing the images consumed by the
nightly automation pipeline.

Pure cosmetic rename of the workflow's top-level name: field; the
filename (build-docker-images.yml) is unchanged so existing schedules,
references, and the new Maintenance: Watchdog matrix all keep working.

Author: igorpecovnik

.github/workflows/build-docker-images.yml

@@ -1,4 +1,4 @@
-name: Docker Images For Repo Handling
+name: Docker Images For Automation
 on:
   push:
     branches: