Bump version to 2.9-git

CHANGELOG.md

-# Master (will become release 2.8)
+# Master (will become release 2.9)
+
+# Release 2.8
 
 * Passing functions that support `f.evaluate(x,y)` to `interpolate()`
   is deprecated. Instead the functions should now provide `operator()`.

dune.module

 Module: dune-localfunctions
-Version: 2.8-git
+Version: 2.9-git
 Author: The Dune Core developers
 Maintainer: dune-devel@lists.dune-project.org
 Description: Provides interface and implementation for shape functions defined on the DUNE reference elements
 URL: https://gitlab.dune-project.org/core/dune-localfunctions
 Python-Requires:
-Depends: dune-geometry (>= 2.8)
+Depends: dune-geometry (>= 2.9)
 Whitespace-Hook: Yes