chore(deps): update dependency black to v26

Author: renovate[bot]

xplainet/pyproject.toml

@@ -25,7 +25,7 @@ requests = "2.25.0"
 matplotlib = "3.3.3"
 pandas = "1.1.4" 
 nb-black = "1.0.7"
-black = "20.8b1"
+black = "26.3.1"
 jupyter_contrib_nbextensions = "0.5.1"
 
 [build-system]