enable and update doxygen (#364)

.github/workflows/doxygen-and-linux-test.yml

@@ -7,7 +7,6 @@ on:
 
 jobs:
   deploy:
-    if: 0
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
@@ -17,7 +16,7 @@ jobs:
       - name: Install Doxygen
         run: |
           sudo apt-get install graphviz doxygen
-          wget https://www.doxygen.nl/files/doxygen-1.11.0.linux.bin.tar.gz
+          wget https://www.doxygen.nl/files/doxygen-1.12.0.linux.bin.tar.gz
           tar -xzf doxygen-*.linux.bin.tar.gz
       
       - name: Generate Doxygen documentation