Mark esp_println as unused to silence warning

It contains our global logger so we need to link against it

src/bin/main.rs

@@ -15,7 +15,7 @@ use esp_hal::clock::CpuClock;
 use esp_hal::spi::master::{Spi, Config as SpiConfig};
 use esp_hal::time::Rate;
 use esp_hal::timer::timg::TimerGroup;
-use esp_println::println;
+#[allow(unused_imports)] use esp_println;  // Needed to link global logger
 use ws2812_rs::{WS2812SPI, SendColorBySPI, Color};
 
 #[panic_handler]