Add doc string to time-stamp-tests that didn't have one

* test/lisp/time-stamp-tests.el (formatz-generate-tests,
  formatz-%z-spotcheck): Add doc strings to tests.
3 jobs for master in 1 minute and 6 seconds (queued for 13 seconds)
Status Job ID Name Coverage
  Fast
failed #23588
test-fast-inotify

00:00:35

 
  Normal
failed #23589
test-lisp-inotify

00:00:28

failed #23590
test-lisp-net-inotify

00:00:28

 
Name Stage Failure
failed
test-lisp-net-inotify Normal There has been a runner system failure, please try again
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
From https://emba.gnu.org/emacs/emacs
* [new ref] 87a432455d7ddc466da55df1ade5a647511740b6 -> refs/pipelines/11465
da200ab..87a4324 master -> origin/master
Checking out 87a43245 as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-2-build-4" is already in use by container "da1fe579c662349f5b0cbedeaf385ca8567e208eca419e08e6d3defd24c4f2dc". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)
failed
test-lisp-inotify Normal There has been a runner system failure, please try again
Using docker image sha256:81f5749c9058a7284e6acd8e126f2b882765a17b9ead14422b51cde1a110b85c for docker:19.03.12 ...
Running on runner-2oEDrUT7-project-1-concurrent-1 via emba.gnu.org...
$ git config --global http.proxy $HTTP_PROXY; git config --global https.proxy $HTTPS_PROXY
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
Checking out 87a43245 as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-1-build-4" is already in use by container "f46df44a43bee1f61a6ede2eac732a4e06eaa2094659f7ea23718f093d67bcc6". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)
failed
test-fast-inotify Fast There has been a runner system failure, please try again
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
From https://emba.gnu.org/emacs/emacs
* [new ref] 87a432455d7ddc466da55df1ade5a647511740b6 -> refs/pipelines/11465
da200ab0..87a43245 master -> origin/master
Checking out 87a43245 as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-1-build-4" is already in use by container "f46df44a43bee1f61a6ede2eac732a4e06eaa2094659f7ea23718f093d67bcc6". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)