Bump clang again

The last attempt didn't work but I'm hopeful that this will based on:

  https://packages.ubuntu.com/search?keywords=libclang&searchon=names&suite=jammy&section=all

.github/workflows/documentation.yml

@@ -21,7 +21,7 @@ jobs:
         run: |
           pip install -r requirements/development.txt
           sudo apt-get -y update
-          sudo apt-get -y install graphviz libclang1-10 libclang-cpp10
+          sudo apt-get -y install graphviz libclang1-11 libclang-cpp11
 
       - name: install doxygen from SF binary archives
         env: