feat: Remove reserved IP feature flag MAASENG-3757 (#5551)

- Removed feature flag conditions for reserved IP features
- Removed flag from `.env`

Resolves [MAASENG-3757](https://warthogs.atlassian.net/browse/MAASENG-3757)

.env

@@ -6,7 +6,4 @@ VITE_BASENAME="/r"
 VITE_APP_BASENAME=${BASENAME}
 VITE_APP_VITE_BASENAME=${VITE_BASENAME}
 VITE_APP_WEBSOCKET_DEBUG=false
-VITE_APP_USABILLA_ID=fd6cf482fbbb
-
-# Feature flags
-VITE_APP_STATIC_IPS_ENABLED=false
+VITE_APP_USABILLA_ID=fd6cf482fbbb

src/app/base/components/IpAssignmentSelect/IpAssignmentSelect.tsx

@@ -22,11 +22,7 @@ export const IpAssignmentSelect = ({
   return (
     <FormikField
       component={Select}
-      help={
-        import.meta.env.VITE_APP_STATIC_IPS_ENABLED === "true"
-          ? "To manage static DHCP leases for a device, go to the address reservation tab of a subnet."
-          : null
-      }
+      help="To manage static DHCP leases for a device, go to the address reservation tab of a subnet."
       label={label}
       options={[
         { label: Labels.DefaultOption, value: "", disabled: true },

src/app/machines/views/MachineDetails/MachineNetwork/NetworkFields/NetworkFields.tsx

@@ -172,11 +172,7 @@ const NetworkFields = ({
       {values.subnet ? (
         <LinkModeSelect
           defaultOption={null}
-          help={
-            import.meta.env.VITE_APP_STATIC_IPS_ENABLED === "true"
-              ? "To manage static DHCP leases for a machine, go to the address reservation tab of a subnet."
-              : null
-          }
+          help="To manage static DHCP leases for a machine, go to the address reservation tab of a subnet."
           interfaceType={interfaceType}
           name="mode"
           onChange={(evt: React.ChangeEvent<HTMLInputElement>) => {

src/app/subnets/views/SubnetDetails/SubnetDetails.tsx

@@ -123,9 +123,7 @@ const SubnetDetails = (): JSX.Element => {
         <Route
           element={
             <>
-              {import.meta.env.VITE_APP_STATIC_IPS_ENABLED === "true" && (
-                <StaticDHCPLease subnetId={id} />
-              )}
+              <StaticDHCPLease subnetId={id} />
               <ReservedRanges subnetId={id} />
             </>
           }