remote: use own/nextcloud URL examples for WebDAV

per #1706 (comment)

content/docs/command-reference/remote/add.md

@@ -343,15 +343,16 @@ $ dvc remote add -d myremote https://example.com/path/to/dir
 ### Click for WebDAV
 
 ```dvc
-$ dvc remote add -d myremote webdavs://example.com/public.php/webdav
+$ dvc remote add -d myremote \
+                    webdavs://example.com/owncloud/remote.php/dav
 ```
 
 If your remote is located in a subfolder of your WebDAV server e.g.
 `/path/to/dir`, this may be appended to the base URL:
 
 ```dvc
 $ dvc remote add -d myremote \
-                    webdavs://example.com/public.php/webdav/path/to/dir
+      webdavs://example.com/owncloud/remote.php/dav/files/USERNAME/
 ```
 
 > See also `dvc remote modify` for a full list of WebDAV parameters.

content/docs/command-reference/remote/modify.md

@@ -640,7 +640,7 @@ more information.
 
   ```dvc
   $ dvc remote modify myremote url \
-        webdavs://example.com/public.php/webdav/path/to/dir
+        webdavs://example.com/nextcloud/remote.php/dav/files/USERNAME/
   ```
 
 - `token` - token for WebDAV server, can be empty in case of using
@@ -660,7 +660,7 @@ more information.
   The order in which DVC searches for username is:
 
   1. `user` parameter set with this command (found in `.dvc/config`);
-  2. User defined in the URL (e.g. `webdav://[email protected]/path`)
+  2. User defined in the URL (e.g. `webdavs://[email protected]/endpoint/path`)
 
 - `password` - password for WebDAV server, can be empty in case of using `token`
   authentication.