Update section on MySQL/MariaDB bacup

[theking2]

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• There is always room for improvement!
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Update Backup — Nextcloud section on MySQL/MariaDB

The official MariaDB documents suggest using mariadb-dump to create backups of a MariaDB database.

To backup MariaDB

```
mariadb-dump --user=[dbuser] --password=[dbpassword] [dbname] > nextcloud-sqlbkp_`date +"%Y%m%d"`.bkp
```

or compress if the database is large

```
mariadb-dump --user=[dbuser] --password=[dbpassword] [dbname] | gzip > nextcloud-sqlbkp_`date +"%Y%m%d"`.bkp.gz
```

To restore MariaDB

```
mariadb --user=[dbuser] --password=[dbpassword] < nextcloud_sqlbkp_.bkp
```

or if compressed

```
gunzip nextcloud_sqlbkp.bkp.gz | mariadb --user=[dbuser] --password=[dbpassword]
```

---

Addressed in #14850

[skjnldsv]

Thanks for flagging this! Unfortunately the issue doesn't include any details about what specifically needs to be updated. If you've found something outdated or incorrect in the MySQL/MariaDB backup section, please reopen with a description of the problem and ideally the corrected command or text.

[skjnldsv]

Oops, my bad, I misread and thought you just quoted the content of the article.
Yes, let's adjust the docs with mariadb-dump! 👍