build: change matrix for maintenance build

Author: foosel

.github/workflows/docs.yaml

@@ -36,9 +36,9 @@ jobs:
             jinja: "3.1.1"
           - version: "maintenance"
             source: "heads"
-            python: "3.10"
-            sphinx: "4.5.0"
-            mermaid: "0.7.1"
+            python: "3.12"
+            sphinx: "8.2.3"
+            mermaid: "1.0.0"
             jinja: "3.1.1"
     steps:
       - name: 🧾 Log event & matrix