Fixed the Helix keymap 'fraanrosi' compile issues (#13514)

According to `helix/rev2/keymaps/fraanrosi/readme.md`, this keymap should be compiled with the following command:

```
make helix/rev2/under:fraanrosi
```

Therefore, when compiling all helix keymaps with the following command, an error occurs when compiling `fraanrosi`.

```
make helix:all
```

Therefore, add `LED_UNDERGLOW_ENABLE = yes` to `keymaps/fraanrosi/rules.mk` to suppress the error.

keyboards/helix/rev2/keymaps/fraanrosi/rules.mk

@@ -20,6 +20,9 @@ EXTRAKEY_ENABLE = yes    # Audio control and System control
 LED_ANIMATIONS = yes        # LED animations
 # IOS_DEVICE_ENABLE = no      # connect to IOS device (iPad,iPhone)
 
+LED_BACK_ENABLE = no
+LED_UNDERGLOW_ENABLE = yes
+
 # convert Helix-specific options (that represent combinations of standard options)
 #   into QMK standard options.
 include $(strip $(KEYBOARD_LOCAL_FEATURES_MK))