workspace: Remove slot property of WindowClone

Since the slot property was only accessed by the old WindowOverlays to
get the position and size of the clone, we can safely stop setting it
and remove that property now.
9 jobs for !1298 with window-clones-merge-overlay in 1 minute and 11 seconds (queued for 2 seconds)
detached
Status Job ID Name Coverage
  Review
failed #750342
check_commit_log

00:00:29

failed #750344
eslint

00:01:10

passed #750343
js_check

00:00:35

passed #750346
no_template_check

00:00:34

passed #750345
potfile_check

00:00:30

 
  Build
skipped #750347
build
skipped #750348
flatpak
flatpak
 
  Test
skipped #750349
test
skipped #750350
test-pot
 
Name Stage Failure
failed
eslint Review
/builds/verdre/gnome-shell/js/misc/util.js:6:29: 'GObject' is assigned a value but never used. Allowed unused vars must match /(^unused|_$)/u. [Error/no-unused-vars]
/builds/verdre/gnome-shell/js/ui/workspace.js:259:52: Missing trailing comma. [Error/comma-dangle]
/builds/verdre/gnome-shell/js/ui/workspace.js:6:7: 'Signals' is assigned a value but never used. Allowed unused vars must match /(^unused|_$)/u. [Error/no-unused-vars]
Running after_script
Uploading artifacts for failed job
Uploading artifacts...
reports: found 4 matching files

Uploading artifacts to coordinator... ok
id=750344 responseStatus=201 Created token=HPZsXhbn
ERROR: Job failed: exit code 1
failed
check_commit_log Review
Running before_script and script
Authenticating with credentials from job payload (GitLab Registry)
$ ./.gitlab-ci/check-commit-log.sh
From https://gitlab.gnome.org/GNOME/gnome-shell
* branch master -> FETCH_HEAD
Missing merge request or issue URL on commit 61d53c7a
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1