at, batch: update pages (#14220)

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>

pages/common/batch.md

@@ -1,17 +1,7 @@
 # batch
 
-> Execute commands at a later time when the system load levels permit.
-> Service atd (or atrun) should be running for the actual executions.
-> More information: <https://manned.org/batch>.
+> This command is an alias of `at`.
 
-- Execute commands from `stdin` (press `Ctrl + D` when done):
+- View documentation for the original command:
 
-`batch`
-
-- Execute a command from `stdin`:
-
-`echo "{{./make_db_backup.sh}}" | batch`
-
-- Execute commands from a given [f]ile:
-
-`batch -f {{path/to/file}}`
+`tldr at`