Do not show Add file button if user has no rights to add files to repo

### Description

Currently button with empty submenu is shown

### Gitea Version

1.17.2

### Can you reproduce the bug on the Gitea demo site?

Yes

### Log Gist

_No response_

### Screenshots

_No response_

### Git Version

_No response_

### Operating System

_No response_

### How are you running Gitea?

Not relevant

### Database

_No response_