docs: fix WinSCP heading underline length

Agent-Logs-Url: https://github.com/nextcloud/documentation/sessions/2c1f4cf0-01aa-4de3-94e3-2d687cf5d98a

Co-authored-by: skjnldsv <14975046+skjnldsv@users.noreply.github.com>

Author: Copilot

user_manual/files/access_webdav.rst

@@ -543,7 +543,7 @@ To get the properties of files in the root folder:
 
 
 Accessing files using WinSCP
-----------------------------
+------------------------------
 
 `WinSCP <https://winscp.net/eng/docs/introduction/>`_ is a free, open-source SFTP,
 FTP, WebDAV, S3, and SCP client for Windows. Its main function is file transfer