Fix missing image in "federated_cloud_sharing.rst"

This adds back the file removed in commit
8106b60025 but still used in
"federated_cloud_sharing.rst".

The remote user shown in the image is
"username@sub.example.com/nextcloud", so the example name used in the
page did not match and thus was removed (it was not replaced as it felt
redundant with the "username" already used in the previous sentence).

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

user_manual/files/federated_cloud_sharing.rst

@@ -14,8 +14,7 @@ by default. Follow these steps to create a new share with other Nextcloud or own
 
 1. Go to your ``Files`` page and click the Share icon on the file or directory 
 you want to share. In the sidebar enter the username and URL of the remote user
-in this form: ``<username>@<oc-server-url>``. In this example, that is
-``layla@remote-server/nextcloud``. The form automatically echoes the address 
+in this form: ``<username>@<oc-server-url>``. The form automatically echoes the address
 that you type and labels it as "remote". Click on the label.
 
 .. figure:: ../images/direct-share-1.png