fix(mono): revert to previous key download

Author: Greelan

mono/latest/Dockerfile

@@ -9,8 +9,10 @@ ARG         DEBIAN_FRONTEND=noninteractive
 
 # Install required packages and Mono
 RUN         set -eux; \
+            apt-get update; \
+            apt-get install -y --no-install-recommends dirmngr; \
             install -d -m 0755 /etc/apt/keyrings; \
-            wget -qO /etc/apt/keyrings/mono-official-archive-keyring.gpg https://download.mono-project.com/repo/xamarin.gpg; \
+            gpg --homedir /tmp --no-default-keyring --keyring /etc/apt/keyrings/mono-official-archive-keyring.gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF; \
             printf 'Types: deb\nURIs: https://download.mono-project.com/repo/debian\nSuites: stable-buster\nComponents: main\nSigned-By: /etc/apt/keyrings/mono-official-archive-keyring.gpg\n' | tee /etc/apt/sources.list.d/mono-official-stable.sources >/dev/null; \
             apt-get update; \
             apt-get install -y mono-complete; \