ci: github: doc-build: avoid Sphinx v6 issue

For some unknown reason, the layout of the Sphinx Tabs extension
in the docset "devicetree" is no longer rendered properly by the
HTML Builder of Sphinx v6. Only cleaning it up and rebuilding it
helps so far.

Signed-off-by: Stephan Linz <linz@li-pro.net>

.github/workflows/doc-build.yml

@@ -94,6 +94,14 @@ jobs:
         run: |
           cmake -B build -GNinja bridle/doc
           ninja -C build build-all
+          #
+          # For some unknown reason, the layout of the Sphinx Tabs extension
+          # in the docset "devicetree" is no longer rendered properly by the
+          # HTML Builder of Sphinx v6. Only cleaning it up and rebuilding it
+          # helps so far.
+          #
+          ninja -C build devicetree-clean
+          ninja -C build devicetree-html
 
       - name: Archive documentation
         working-directory: workspace/build