Update Doxygen to use latest ubuntu version and updated config file. (#…

…234)

* Initialise variables in test before use

* Init variables in serializer tests

* Update uncrustify runner OS version

* Update doxygen config and doxygen used to latest

* Update brief and remove unused return description

* Update python version for latest ubuntu image

.github/workflows/ci.yml

@@ -47,7 +47,7 @@ jobs:
           path: ./
           horrid_threshold: 10
   doxygen:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - name: Run doxygen build
@@ -111,7 +111,7 @@ jobs:
       - name: Install Python3
         uses: actions/setup-python@v2
         with:
-          python-version: '3.7.10'
+          python-version: '3.11.0'
       - name: Measure sizes
         uses: FreeRTOS/CI-CD-Github-Actions/memory_statistics@main
         with: