Fixes repo server gp2/gp3 discrepency

TO be retagged v3.1.1

base/repo_server/main.tf

@@ -51,7 +51,7 @@ resource "aws_instance" "instance" {
 
   # These device definitions are optional, but added for clarity.
   root_block_device {
-      volume_type = "gp2"
+      volume_type = "gp3"
       #volume_size = "60"
       delete_on_termination = true
       encrypted = true