Revert to Doxygen 1.11 for now #24

Just until #24 is resolved.

Author: pcolby

.github/workflows/docs.yaml

@@ -6,7 +6,7 @@ permissions:
   contents: read
 
 env:
-  DOXYGEN_VERSION: 1.12.0
+  DOXYGEN_VERSION: 1.11.0
 
 jobs:
   generate: