lockin: remove SPI error ISR

Let them be handled by HardFault here.
Keep them in dual-iir for debugging and show-casing their usage.

src/bin/lockin.rs

@@ -307,26 +307,6 @@ const APP: () = {
         unsafe { hal::ethernet::interrupt_handler() }
     }
 
-    #[task(binds = SPI2, priority = 3)]
-    fn spi2(_: spi2::Context) {
-        panic!("ADC0 SPI error");
-    }
-
-    #[task(binds = SPI3, priority = 3)]
-    fn spi3(_: spi3::Context) {
-        panic!("ADC1 SPI error");
-    }
-
-    #[task(binds = SPI4, priority = 3)]
-    fn spi4(_: spi4::Context) {
-        panic!("DAC0 SPI error");
-    }
-
-    #[task(binds = SPI5, priority = 3)]
-    fn spi5(_: spi5::Context) {
-        panic!("DAC1 SPI error");
-    }
-
     extern "C" {
         // hw interrupt handlers for RTIC to use for scheduling tasks
         // one per priority