Run black via poetry in pre-commit-hook

This is the preferred way, as it ensures that the right virtual
environment is active, see other qc repos.

Signed-off-by: Pierre R. Mai <pmai@pmsf.de>

Author: pmai

.pre-commit-config.yaml

@@ -9,6 +9,6 @@ repos:
     hooks:
       - id: black
         name: black
-        entry: black
+        entry: poetry run black
         language: system
         types: [python]