make deploy: Go back to deleting any pre-existing files on the server

We stopped doing this back in commit
0bce98367c70c43eaa425aad101e15ed3db612a8 specifically because I was
concerned about a deployment of the top-level "lmno.games" content
obliterating lower-level content (such as that deployed by the
"empires-html" repository).

But now, I've switched to hosting the empires HTML content in this
same repository where it will be deployed together. And that's my plan
going forward, to house all static HTML content here in this
lmno.games repository. So in this commit we start passing the --delete
flag to rsync again.

The one exception is the "flempires" directory where Kevin is
currently experimenting. In the future, we'll likely incorporate that
content into this repository as well. But for now, we simply
explicitly exclude it so that deployments here won't destroy anything
he has deployed there.

0bce98367c70c43eaa425aad101e15ed3db612a8#