remove BLE from feature key

Author: Qinghao Shi

tools/test/examples/examples.json

@@ -75,7 +75,7 @@
             "BLE_SM",
             "BLE_Thermometer"
       ],
-      "features" : ["BLE"],
+      "features" : [],
       "targets" : ["NRF51_DK", "NRF52_DK", "DISCO_L475VG_IOT01A"],
       "toolchains" : [],
       "exporters": [],