Remove IAR from list of supported toolchains

Author: harrisonmutai-arm

targets/targets.json

@@ -6325,8 +6325,7 @@
         ],
         "supported_toolchains": [
             "GCC_ARM",
-            "ARM",
-            "IAR"
+            "ARM"
         ],
         "device_has": [
             "USTICKER",
@@ -6624,8 +6623,7 @@
         ],
         "supported_toolchains": [
             "GCC_ARM",
-            "ARM",
-            "IAR"
+            "ARM"
         ],
         "device_has": [
             "ANALOGIN",