package.json: update json-rpc2 and lodash for security update

This was part of https://go-review.googlesource.com/c/vscode-go/+/241041
but we are submitting it as a separate cl.

Fixes issues reported by security issues reported by npm audit.

 npm install --save json-rpc2
 npm update lodash --depth 3

json-rpc2@2.0.0 was released recently, so instead of switching to
vscode-jsonrpc, we are updating to the newest version.

Also updated the extension version 0.16.0-dev to reflect the current dev cycle.

Updates #113

Change-Id: I6a4aae5293fd505ca1ad9c39e485c3adf41c2dec
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/241557
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "go",
   "displayName": "Go",
-  "version": "0.15.1-dev",
+  "version": "0.16.0-dev",
   "publisher": "golang",
   "description": "Rich Go language support for Visual Studio Code",
   "author": {
@@ -49,7 +49,7 @@
     "deep-equal": "^2.0.2",
     "diff": "^4.0.2",
     "glob": "^7.1.6",
-    "json-rpc2": "^1.0.2",
+    "json-rpc2": "^2.0.0",
     "moment": "^2.24.0",
     "semver": "^7.3.2",
     "tree-kill": "file:third_party/tree-kill",