Merge branch 'hchouraria-docs-improve-background-migrations-pending-command' into 'master'

Change pending jobs command to print count

See merge request gitlab-org/gitlab!79601

doc/update/index.md

@@ -98,7 +98,7 @@ that can process jobs in the `background_migration` queue.
 
 ```shell
 sudo gitlab-rails runner -e production 'puts Gitlab::BackgroundMigration.remaining'
-sudo gitlab-rails runner -e production 'puts Gitlab::Database::BackgroundMigrationJob.pending'
+sudo gitlab-rails runner -e production 'puts Gitlab::Database::BackgroundMigrationJob.pending.count'
 ```
 
 **For installations from source:**