Use latest version of darker that resolves imcompatibility with `black` library.

.github/workflows/darker.yml

@@ -16,7 +16,7 @@ jobs:
       - uses: actions/setup-python@v4
         with:
           python-version: '3.7'
-      - uses: akaihola/darker@1.5.1
+      - uses: akaihola/darker@1.6.1
         with:
           options: "--check --diff --isort"
-          version: "@3c675b009d747cadd6e8048d2c57a5b1cd54fb3e"
+          version: "1.6.1"

.pre-commit-config.yaml

@@ -39,7 +39,7 @@ repos:
       - id: check-vcs-permalinks
 
   - repo: https://github.com/akaihola/darker
-    rev: 3c675b009d747cadd6e8048d2c57a5b1cd54fb3e
+    rev: 1.6.1
     hooks:
     -   id: darker
         args: [--isort]