esp32: Don't put py/scheduler.o in iRAM, it's no longer needed.

ISR's no longer need to be in iRAM, and the ESP IDF provides an option to
specify that they are in iRAM if an application needs lower latency when
handling them.  But we don't use this feature for user interrupts: both
timer and gpio ISR routines are registered without the ESP_INTR_FLAG_IRAM
option, and so the scheduling code no longer needs to be in iRAM.