samples: display: lvgl: Fix README.rst

The commands still refer to the old directory name 'gui' instead of
'display'.

Signed-off-by: Detlev Zundel <[email protected]>

Author: laodzu

samples/display/lvgl/README.rst

@@ -49,15 +49,15 @@ Building and Running
 Example building for :ref:`nrf52840dk_nrf52840`:
 
 .. zephyr-app-commands::
-   :zephyr-app: samples/gui/lvgl
+   :zephyr-app: samples/display/lvgl
    :board: nrf52840dk_nrf52840
    :shield: adafruit_2_8_tft_touch_v2
    :goals: build flash
 
 Example building for :ref:`native_posix`:
 
 .. zephyr-app-commands::
-   :zephyr-app: samples/gui/lvgl
+   :zephyr-app: samples/display/lvgl
    :board: native_posix
    :goals: build flash