Bump Python requirement mkdocs-section-index to 0.3.9

pyproject.toml

@@ -62,7 +62,7 @@ docs = [
     "mkdocs-gen-files==0.5.0",
     "mkdocs-literate-nav==0.6.1",
     "mkdocs-material==9.5.31",
-    "mkdocs-section-index==0.3.8",
+    "mkdocs-section-index==0.3.9",
     "mkdocstrings-python==1.10.7",
 ]