Rename "Download" button to "Upload" in plugin admin page

[erdnaxe]

Describe the bug
In ADMIN > PLUGINS, the DOWNLOAD button is used to send a gem to the COSMOS server.
The terminology is not intuitive for the user, usually client->server is called uploading in web software.

To Reproduce
Steps to reproduce the behavior:

1. Click 'ADMIN'
2. Click on 'PLUGINS'
3. Observe the dark blue bar containing the "DOWNLOAD" button.

Expected behavior

1. Click 'ADMIN'
2. Click on 'PLUGINS'
3. Observe the dark blue bar containing the "UPLOAD" button.

Environment (please complete the following information):

• OS: NixOS 22.05, using cosmos-control.sh with Docker.
• COSMOS Version [e.g. 4.0.0] 5.0.5
• Cosmos v5
  • Google Chrome 106.0.5249
  • Mozilla Firefox 106.0.1