Bump string_decoder@^1.2.0 (#5536)

Author: compulim

samples/01.getting-started/k.direct-line-token/javascript/bot/package-lock.json

@@ -19,6 +19,11 @@
     ]
   },
   "overrides": {
+    "hpack.js": {
+      "readable-stream": {
+        "string_decoder": "^1.2.0"
+      }
+    },
     "restify": {
       "find-my-way": "^8.2.2",
       "send": "^0.19.1"