Remove nanostack border router from examples list

nanostack border router is now owned by ISG and has been moved
out of ARMmbed and into their organisation. ISG will be
responsible for updating and testing this example going forward.

tools/test/examples/examples.json

@@ -127,20 +127,6 @@
       "compare_log": ["mbed-os-example-wifi/tests/wifi_scan.log"],
       "auto-update" : true
     },
-    {
-      "name": "nanostack-border-router",
-      "github":"https://github.com/ARMmbed/nanostack-border-router",
-      "sub-repo-example": false,
-      "subs": [],
-      "features" : [],
-      "targets" : ["K66F", "NUCLEO_F429ZI"],
-      "toolchains" : [],
-      "exporters": [],
-      "compile" : true,
-      "export": true,
-      "test" : false,
-      "auto-update" : true
-    },
     {
       "name": "mbed-os-example-cellular",
       "github":"https://github.com/ARMmbed/mbed-os-example-cellular",