Update readme_v2.md (#15656)

Under demo.items the button-last-event channel was of the Number type. I have changed this to String.
In the channels for devices section this was already corrected but is not 'live' yet?

Signed-off-by: Gemertw <59452423+Gemertw@users.noreply.github.com>

bundles/org.openhab.binding.hue/doc/readme_v2.md

@@ -225,7 +225,7 @@ Color Living_Room_Standard_Lamp_Left_Colour "Living Room Standard Lamp Left Colo
 Dimmer Living_Room_Standard_Lamp_Left_Brightness "Living Room Standard Lamp Left Brightness [%.0f %%]" {channel="hue:device:g24:11111111-2222-3333-4444-555555555555:brightness"}
 Switch Living_Room_Standard_Lamp_Left_Switch "Living Room Standard Lamp Left Switch" (g_Lights_On_Count) {channel="hue:device:g24:11111111-2222-3333-4444-555555555555:switch"}
 
-Number Kitchen_Wallplate_Switch_Last_Event "Kitchen Wallplate Switch Last Event" {channel="hue:device:g24:11111111-2222-3333-4444-666666666666:button-last-event"}
+String Kitchen_Wallplate_Switch_Last_Event "Kitchen Wallplate Switch Last Event" {channel="hue:device:g24:11111111-2222-3333-4444-666666666666:button-last-event"}
 Switch Kitchen_Wallplate_Switch_Battery_Low_Alarm "Kitchen Wallplate Switch Battery Low Alarm" {channel="hue:device:g24:11111111-2222-3333-4444-666666666666:battery-low"}
 ```