runtime/nrf: remove some leftover header files

src/runtime/nrfx_config.h

@@ -1,4 +0,0 @@
-
-#pragma once
-
-#define NRFX_ASSERT(expression) do { bool res = expression; (void)res; } while (0)

src/runtime/runtime_nrf.h

@@ -1,6 +0,0 @@
-
-#pragma once
-
-#include <stdint.h>
-
-void rtc_sleep(uint32_t ticks);