[doc] Add some words in changelog about pyramid support in core + fix its title
Closes #16121152.
3.24
====
New features
------------
* Various bits of a CubicWeb application configuration can be now be
overridden through environments variables matching configuration option
names prefixed by ``CW_`` (for instance ``CW_BASE_URL``).
* Cubes are now standard Python packages named as ``cubicweb_<cubename>``.
They are not anymore installed in ``<prefix>/share/cubicweb/cubes``. Their
discovery by CubicWeb is handled by a new setuptools entry point
``cubicweb.cubes``. A backward compatibility layer is kept for "legacy"
cubes.
* Pyramid support made it into CubicWeb core. Applications that use it
should now declare the `cubicweb[pyramid]` dependency instead of
`cubicweb-pyramid`.