📦📝 Allow modern Towncrier in docs builds

sphinx-contrib/sphinxcontrib-towncrier#92
has been resolved and the recent Towncrier versions are compatible
with the `sphinxcontrib.towncrier` Sphinx extension project yet again.

Author: webknjaz

doc/en/broken-dep-constraints.txt

@@ -1,6 +1,2 @@
 # This file contains transitive dependencies that need to be pinned for some reason.
 # Eventually this file will be empty, but in this case keep it around for future use.
-
-# Pin towncrier temporarily due to incompatibility with sphinxcontrib-towncrier:
-# https://github.com/sphinx-contrib/sphinxcontrib-towncrier/issues/92
-towncrier<24.7