ci: add mono via apt

Author: YOU54F

.github/workflows/build-test-publish.yml

@@ -75,9 +75,9 @@ jobs:
             /usr/share/keyrings/mono-official-archive-keyring.gpg \
             --keyserver hkp://keyserver.ubuntu.com:80 \ 
             --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF \
-             echo "deb [signed-by=/usr/share/keyrings/mono-official-archive-keyring.gpg] https://download.mono-project.com/repo/debian stable-buster main" | sudo tee /etc/apt/sources.list.d/mono-official-stable.list
-           sudo apt update
-           sudo apt install -y mono-complete
+            echo "deb [signed-by=/usr/share/keyrings/mono-official-archive-keyring.gpg] https://download.mono-project.com/repo/debian stable-buster main" | sudo tee /etc/apt/sources.list.d/mono-official-stable.list
+          sudo apt update
+          sudo apt install -y mono-complete
           
 
       - name: Publish to Nuget