bsp(feather_m4)!: Fixes a minor compiler warning in the adc example.

Author: kyp44

boards/feather_m4/examples/adc.rs

@@ -17,7 +17,7 @@ use bsp::Pins;
 use pac::{CorePeripherals, Peripherals};
 
 use hal::{
-    adc::{Accumulation, Adc, Prescaler, Resolution},
+    adc::{Accumulation, Prescaler},
     clock::v2::{clock_system_at_reset, pclk::Pclk},
 };