[uploading-files.xml]: Remove reference to Dashboard Collections pane, add curl example

[joewiz]

Describe the problem

The Uploading Files into eXist-db article still references using the Collections pane of the Dashboard. This should be removed.

Furthermore, I think a sample curl command demonstrating the use of the REST interface would be nice to add:

curl -s -f -H 'Content-Type: application/xml' \
     -T <filename> \
     --user <user>:<password> \
     "http://localhost:8080/exist/rest/db/apps/<collection>/<filename>"

Screenshots

n/a

Please provide the following

• exist-db version: 5.3.0
• documentation version: current develop