[Taler] LibEuFin versioning

[José Carlos Micó]

It is unclear which is the latest stable release for LibEuFin looking at 
git repo, there are 34 tags for 0.9.3-dev.* release, while Taler 0.9.3 
was released on 2023-11-30.

At some point of 0.9.3-dev the Makefile was updated to include `make 
install-nobuild-*` targets, rendering `install-bank` and `install-nexus` 
obsolete. Those are the targets on master branch and LibEuFin 0.9.3 
release at ftp.gnu.org

It seems pretty safe to change docs as shown below:

  $ make compile
  # make install-nobuild-*

Furthermore, there are some broken links at
https://taler.net/en/news/2023-11.html (actual links are also given)

  - http://ftpmirror.gnu.org/taler/libeufin-0.9.3.tar.gz
  - http://ftpmirror.gnu.org/taler/libeufin-0.9.3.tar.gz.sig

  + http://ftpmirror.gnu.org/taler/libeufin-0.9.3-sources.tar.gz
  + http://ftpmirror.gnu.org/taler/libeufin-0.9.3-sources.tar.gz.sig