docs(i2c-controller): slightly expand the test README

tests/i2c-controller/README.md

@@ -3,12 +3,13 @@
 ## About
 
 This application is testing raw I2C bus usage in RIOT-rs.
-Please use `riot_rs::sensors` instead for a high-level sensor abstraction that is architecture-agnostic.
 
 ## How to run
 
 In this folder, run
 
     laze build -b nrf52840dk run
 
-This example requires a LIS3DH sensor (3-axis accelerometer) attached to the pins configured in the test.
+This test requires an LIS3DH sensor (3-axis accelerometer) attached to the pins configured in the
+`pins` module.
+It attempts to read the `WHO_AM_I` register and checks the received value against the expected id.