Fix a parse error at targets/targets.json.

Author: soramame21

targets/targets.json

@@ -1352,7 +1352,7 @@
         "macros_add": ["USBHOST_OTHER"],
         "device_has_add": ["ANALOGOUT", "CAN", "LOWPOWERTIMER", "SERIAL_FC", "TRNG", "FLASH"],
         "release_versions": ["2", "5"],
-        "device_name": "STM32L476VG"
+        "device_name": "STM32L476VG",
         "bootloader_supported": true
     },
     "MTS_MDOT_F405RG": {