CI: Fix directory name for published prod docs
- [X] xref #48211 

The job to publish the docs to our production server when a new tag is created worked mostly fine for the 1.5.0 release. The only thing is that the tag name is `v1.5.0`, while the docs had to be published to the `1.5.0` directory (without the heading `v`). Fixing this here, so docs are published to the right directory.
I think we should backport for the 1.5.x releases