Remove attachments from the Themes Trac

[poena]

The problem:
Authors are using the attach file functionality in their Trac tickets
to attach zip files with theme updates, instead of using the correct upload form.

Suggested solution:
Remove/hide the attachment functionality.

Add information about and link to the upload page ​https://wordpress.org/themes/upload/
in the ticket interface.

[Otto42]

The attachment functionality is useful for communicating with theme authors by being able to post screenshots and other things to convey the information needed.

So, I wouldn't agree with removing it, however maybe just changing the attachment interface to have some text on it explaining things would make more sense.

[joyously]

Or don't allow zip files.

[Otto42]

Hmm. Not a bad idea. I'll have to delve into Trac more to figure that out.

[dd32]

In 7890:

Trac: Block uploading of ZIPs to themes.trac.wordpress.org and display a notice directing them to the Theme upload form.

This can be bypassed, but is a much simpler solution than modifying Trac.

Fixes #3904.

[dd32]

In 7891:

Trac: Bump scripts version following [7890].

See #3904.