fix: Remove the fact that items in HTTP responses can be null (#1132

)

See kumahq/kuma#6639 (specifically kumahq/kuma#6639 (comment)) and kumahq/kuma#6648

I'm guessing there are a load of places where we no longer need null guards anymore. I haven't gone through and amended if there are as I'm guessing these will eventually be removed during natural tech debt work.

Signed-off-by: John Cowen <john.cowen@konghq.com>

src/types/api.d.ts

@@ -8,7 +8,7 @@
  * ```
  */
 export interface ApiListResponse<ResourceType> {
-  items: ResourceType[] | null
+  items: ResourceType[]
   total: number
 }