docs(ins): remove outdated concept

Author: bene2k1

pages/instances/concepts.mdx

@@ -64,18 +64,6 @@ An Instance is a virtual computing unit that offers resources for running applic
 
 An InstantApp is an image with a preinstalled application. By choosing an InstantApp when prompted to select an image during the [creation of your Instance](/instances/how-to/create-an-instance/), you choose to install the specified application on your Instance. You can then start using the application immediately.
 
-## IP mobility
-
-The legacy public network is provided through carrier-grade NAT infrastructure.
-When an Instance starts, it is assigned a NAT IP address that is associated with the underlying node hosting the Instance.
-The carrier-grade NAT establishes a one-to-one mapping between the public IP and the NAT IP assigned to the Instance during provisioning. Consequently, if the underlying node changes, the NAT IP address will also change.
-
-With IP mobility, there are no NAT IPs anymore. The public IP is entirely routed to the Instance. The main benefit is that your underlying IP no longer changes when you stop and start your Instance or if it gets provisioned on another hypervisor. But this also means that if you do not attach a public IP address to your Instance, then it will not have any network access.
-
-<Message type="note">
-  Your IP address will only be retained during stop/start operations if you have linked a flexible public IP address to your Instance. If you use a dynamic IP address, the behavior remains consistent, whether your Instance has a routed IP enabled or is a legacy one.
-</Message>
-
 ## Learning Instance
 
 [Learning Instances](https://www.scaleway.com/en/stardust-instances/) are the perfect Instances for small workloads and simple applications. You can create up to one Instance per Availability Zone (available in FR-PAR-1 and NL-AMS-1).
@@ -134,7 +122,7 @@ Reverse DNS is the opposite of classic "forward" DNS, and maps an IP address to
 
 ## Routed flexible IP
 
-A routed flexible IP means assigning a public IP address to an Instance (virtual machine) that is reachable directly from the internet. This means there's [no address translation](/instances/concepts/#carrier-grade-nat-cgnat), and the Instance uses the public IP as its identity on the internet.
+A routed flexible IP means assigning a public IP address to an Instance (virtual machine) that is reachable directly from the internet. This means there's no address translation, and the Instance uses the public IP as its identity on the internet.
 The Instance can be accessed or can communicate directly using this public IP, which helps to make network configuration straightforward, with unrestricted inbound and outbound connections, crucial for services like web hosting or email servers.
 
 ## Security group