package.json: update dev version

For #2252

Change-Id: Ibdf8315d35995dc6edafdb1742421168795890a9
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/413416
Run-TryBot: Suzy Mueller <[email protected]>
Reviewed-by: Dylan Le <[email protected]>
TryBot-Result: kokoro <[email protected]>

Author: suzmue

package-lock.json

@@ -1,7 +1,7 @@
 {
   "name": "go",
   "displayName": "Go",
-  "version": "0.34.0-dev",
+  "version": "0.35.0-dev",
   "preview": true,
   "publisher": "golang",
   "description": "Rich Go language support for Visual Studio Code",