ci: don't build devel docs anymore

Author: foosel

.github/workflows/docs.yaml

@@ -40,12 +40,6 @@ jobs:
             sphinx: "4.5.0"
             mermaid: "0.7.1"
             jinja: "3.1.1"
-          - version: "devel"
-            source: "heads"
-            python: "3.10"
-            sphinx: "4.5.0"
-            mermaid: "0.7.1"
-            jinja: "3.1.1"
     steps:
       - name: 🧾 Log event & matrix
         run: |