samples: instrumentation: remove unnecessary include of instrumentation.h

The instrumentation.h header is not needed to compile the
instrumentation sample and it can be misleading for folks to think they
have to include it in their code to use the subsystem, so remove it.

Signed-off-by: Benjamin Cabé <[email protected]>

Author: kartben

samples/subsys/instrumentation/src/main.c

@@ -5,7 +5,6 @@
  */
 
 #include <zephyr/kernel.h>
-#include <zephyr/instrumentation/instrumentation.h>
 
 #define SLEEPTIME 10
 #define STACKSIZE 1024