fix(examples): run apt-get update before installing packages

Author: kangasta

examples/create_and_restore_backup.md

@@ -31,7 +31,8 @@ To have something to backup, we will install a nginx server and configure a non-
 ```sh filename=configure-nginx.sh
 #!/bin/sh -xe
 
-apt install nginx -y
+apt-get update
+apt-get install nginx -y
 echo "Hello from $(hostname)"'!' > /var/www/html/index.html
 ```
 

examples/use_userdata_to_configure_server.md

@@ -13,7 +13,8 @@ First, create a file for the user-data script. The script installs [podman](http
 
 ```sh filename=user-data.sh
 #!/bin/sh
-sudo apt install -y podman
+sudo apt-get update
+sudo apt-get install -y podman
 podman run -d -p 80:80 ghcr.io/upcloudltd/hello
 ```