KW24D: Use default ARM compiler (ARMC6)

KW24D was set to ARMC5 because the ARMC6 tooling didn't correctly handle
Cortex-M4 without floating-point. Now fixed.

Author: kjbracey

targets/targets.json

@@ -1347,7 +1347,7 @@
     "KW24D": {
         "supported_form_factors": ["ARDUINO"],
         "core": "Cortex-M4",
-        "supported_toolchains": ["ARMC5", "GCC_ARM", "IAR"],
+        "supported_toolchains": ["ARM", "GCC_ARM", "IAR"],
         "extra_labels": ["Freescale", "MCUXpresso_MCUS", "KSDK2_MCUS", "FRDM"],
         "is_disk_virtual": true,
         "macros": ["CPU_MKW24D512VHA5", "FSL_RTOS_MBED"],