extension/package.json: update version to 0.48.0-dev

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

Change-Id: I8cab906d6981592a81a42cfd21ddb0b2f2569764
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/653416
Reviewed-by: Hongxiang Jiang <hxjiang@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Madeline Kalil <mkalil@google.com>
Auto-Submit: Gopher Robot <gobot@golang.org>
kokoro-CI: kokoro <noreply+kokoro@google.com>

Author: gopherbot

extension/package-lock.json

@@ -1,7 +1,7 @@
 {
   "name": "go",
   "displayName": "Go",
-  "version": "0.46.0-dev",
+  "version": "0.48.0-dev",
   "publisher": "golang",
   "description": "Rich Go language support for Visual Studio Code",
   "author": {