WSDCGQ11LM.md: Adjust pairing instructions (Koenkk#2987)

This PR clarifies that the reset button has to be released immediatly
after the blue LED starts blinking.

This has been reported here:
  Koenkk/zigbee2mqtt#21332

Signed-off-by: Christoph Müllner <[email protected]>

Author: cmuellner

docs/devices/WSDCGQ11LM.md

@@ -29,8 +29,8 @@ pageClass: device-page
 Uses a CR2032 battery
 
 ### Pairing
-Press and hold the reset button on the device for +- 5 seconds (until the blue light starts blinking).
-After this the device will automatically join. If this doesn't work, try with a single short button press.
+Press and hold the reset button on the device for +- 5 seconds (when the blue blinks, immediately release the button for pairing to start).
+After this, the device will automatically join. If this doesn't work, try with a single short button press.
 
 ![WSDCGQ11LM pairing](../images/pairing/WSDCGQ11LM_pairing.jpg)