zeroproedbg.json fixed

Author: sebba

hardware/arduino/samd/opt/boards/0020.zeroproedbg.json

@@ -20,7 +20,7 @@
     "usb_product" : "Arduino M0 Pro",
     "board": "SAM_ZERO",
     "core": "arduino",
-    "extra_flags": "-D__SAMD21G18A__ -mthumb ",
+    "extra_flags": "-D__SAMD21G18A__ -mthumb",
     "ldscript": "linker_scripts/gcc/flash_with_bootloader.ld",
     "openocdscript": "openocd_scripts/arduino_zero.cfg",
     "variant": "arduino_zero",