[DOC] inconsistency with my_backup examples

[LeeDr]

Elasticsearch version (bin/elasticsearch --version): Docs issue with
https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-snapshots.html

Description of the problem including expected versus actual behavior:

The Repositories section includes a few examples referencing my_backup like
PUT /_snapshot/my_backup
and
GET /_snapshot/my_backup

But in the Shared File System Repository section it keeps referring to my_backup in the text but isn't using that in the examples so it makes it rather confusing;

"... This location (or one of its parent directories) must be registered in the path.repo setting on all master and data nodes.
Assuming that the shared filesystem is mounted to /mount/backups/my_backup, the following setting should be added to elasticsearch.yml file:"

path.repo: ["/mount/backups", "/mount/longterm_backups"]

And again here. It looks like maybe my_backup was changed to my_fs_backup but I don't know snapshots very well so I could me misinterpreting it.

"After all nodes are restarted, the following command can be used to register the shared file system repository with the name my_backup:"

PUT /_snapshot/my_fs_backup
{

And then a few more examples alternate between my_backup and my_fs_backup;

GET /_snapshot/my_backup/_current
DELETE /_snapshot/my_backup/snapshot_2
DELETE /_snapshot/my_fs_backup
POST /_snapshot/my_backup/snapshot_1/_restore

[elasticmachine]

Pinging @elastic/es-distributed

[tlrx]

Thanks @LeeDr, I created #30480