GHA: Add missing libfmt dependency in doxygen workflow

Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>

Author: flichtenheld

.github/workflows/doxygen.yml

@@ -25,7 +25,7 @@ jobs:
           sudo apt update
           sudo apt install -y --no-install-recommends \
             build-essential cmake doxygen graphviz ninja-build \
-            libasio-dev libcap-dev liblz4-dev libjsoncpp-dev libssl-dev libxxhash-dev
+            libasio-dev libcap-dev libfmt-dev libjsoncpp-dev liblz4-dev libssl-dev libxxhash-dev
 
       - name: Build Doxygen documentation
         id: build