[release-v0.50]extension/package.json: update version to 0.50.0

This is an automated CL which updates the package.json and package-lock.json.

Change-Id: Iaf1d4c344cc5e4d3b3f49de9cda06c37af250945
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/700737
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Madeline Kalil <[email protected]>
Auto-Submit: Gopher Robot <[email protected]>
Reviewed-by: Hongxiang Jiang <[email protected]>

Author: gopherbot

extension/package-lock.json

@@ -1,7 +1,7 @@
 {
   "name": "go",
   "displayName": "Go",
-  "version": "0.50.0-dev",
+  "version": "0.50.0",
   "publisher": "golang",
   "description": "Rich Go language support for Visual Studio Code",
   "author": {