[client-python] chore(deps): update dependency black to v26

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

pyproject.toml

@@ -47,7 +47,7 @@ dependencies = [
 
 [project.optional-dependencies]
 dev = [
-    "black (>=25.11.0,<25.12.0)",
+    "black (>=26.3.1,<26.4.0)",
     "build (>=1.3.0,<1.4.0)",
     "isort (>=8.0.1,<8.1.0)",
     "types-pytz (>=2025.2.0.20250326,<2025.3.0.0)",