Upgrade to Debian 11 and use default repositories

Vagrantfile

@@ -1,6 +1,11 @@
 Vagrant.configure("2") do |config|
-  config.vm.box = "debian/contrib-buster64"
+  config.vm.box = "debian/bullseye64"
   config.vm.synced_folder ".", "/vagrant"
   config.vm.network "private_network", type: "dhcp"
-  config.vm.provision "shell", path: "install-docker.sh"
+  config.vm.provision "shell", inline: <<-SHELL
+    apt-get update
+    apt-get install -y docker.io docker-compose
+    dd if=/dev/zero of=/EMPTY bs=1M
+    rm -f /EMPTY
+  SHELL
 end