use installed version in sphinx

doc/conf.py

@@ -18,10 +18,8 @@
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
 import os
-import sys
 from typing import List
 
-sys.path.insert(0, os.path.abspath("../"))
 from ess import __version__
 
 # -- General configuration ------------------------------------------------