fix: [M3-7270] - Edit Linode VLAN config interface (#9798)

## Description 📝
Bug from #9709

On the prod env, we were unable to edit a config due to the config interface being deleted. This was due to the `regionHasVPCs` variable being coupled with `regionHasVLANS` in the if statement to delete config interfaces. The fix was to handle VPCs and VLANs separately.

## How to test 🧪

### Prerequisites
- Point to the prod environment

### Reproduction steps
- Go to a Linode's details page and click on the `Configurations` tab
- Click the edit button and scroll down to the Networking section
- Select a VLAN and save changes

### Verification steps 
- The VLAN changes should be reflected in the Configurations table

packages/manager/src/features/Linodes/LinodesDetail/LinodeConfigs/LinodeConfigDialog.tsx

@@ -368,8 +368,16 @@ export const LinodeConfigDialog = (props: Props) => {
       configData.initrd = finnixDiskID;
     }
 
-    if (!regionHasVLANS || !regionHasVPCs) {
-      delete configData.interfaces;
+    if (!regionHasVLANS) {
+      configData.interfaces = configData.interfaces?.filter(
+        (_interface) => _interface.purpose !== 'vlan'
+      );
+    }
+
+    if (!regionHasVPCs) {
+      configData.interfaces = configData.interfaces?.filter(
+        (_interface) => _interface.purpose !== 'vpc'
+      );
     }
 
     const actionType = Boolean(config) ? 'updated' : 'created';