example: Fix defined pin for sensor in BeamSensor sketch

Fixed the defined pin for the BeamSensor1 based on the current HW.
diff --git a/examples/BeamSensor/BeamSensor.ino b/examples/BeamSensor/BeamSensor.ino
index c752a9d..7fcd7e5 100644
--- a/examples/BeamSensor/BeamSensor.ino
+++ b/examples/BeamSensor/BeamSensor.ino
@@ -11,7 +11,7 @@
 
 #define BEAM_SENSOR_1_ID      1
 #define BEAM_SENSOR_1_NAME    "Beam Sensor 1"
-#define BEAM_SENSOR_1_PIN     3
+#define BEAM_SENSOR_1_PIN     2
 
 #define BEAM_SENSOR_2_ID      2
 #define BEAM_SENSOR_2_NAME    "Beam Sensor 2"