samples: mesh_badge: fix temperature format

The sensor API returns the temperature in celsisus degree. The Bluetooth
temperature characteristics uses M = 1, d = -2, b = 0, which corresponds
to a resolution of 0.01 degree. This means that the value returned by
sensor_value_to_double has to be multiplied by 100.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>