teensy40: fix typo in target JSON

targets/teensy40.json

@@ -8,7 +8,7 @@
   "cflags": [
     "--target=armv7em-none-eabi",
     "-Qunused-arguments",
-    "-mfloat-abi=soft",
+    "-mfloat-abi=soft"
   ],
   "linkerscript": "targets/mimxrt1062-teensy40.ld",
   "extra-files": [