Default to x86_64 for mongotools

A recent change made to support arm64 has broken mongodb
backups for users on amd64 architecture.

This is because mongotools has no file named 
[...]-ubuntu2004-amd64-100.6.1.deb.
This file is actually called 
[...]-ubuntu2004-x86_64-100.6.1.deb.

This change will make x86_64 the default architecture, 
and will only switch to arm64 (which does exist) if 
umode -m returns arm64 or aarch64.

docker/Dockerfile

@@ -19,10 +19,8 @@ ENV PATH="${PATH}:/root/.poetry/bin"
 
 # Install mongotools, used for getting mongo backups
 RUN <<-EOF
-architecture=""
+architecture="x86_64"
     case $(uname -m) in
-        x86_64) architecture="amd64" ;;
-        x86_64) architecture="amd64" ;;
         arm64) architecture="arm64" ;;
         aarch64) architecture="arm64" ;;
     esac