package.json: set virtualWorkspaces capability to false

Go and many tools don't work in virtual workspaces.

Fixes #1483

Change-Id: I56120e9ca07420ee4723f038f76f595866bf36b9
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/320430
Trust: Hyang-Ah Hana Kim <[email protected]>
Run-TryBot: Hyang-Ah Hana Kim <[email protected]>
TryBot-Result: kokoro <[email protected]>
Reviewed-by: Rebecca Stambler <[email protected]>

Author: hyangah

package.json

@@ -103,6 +103,7 @@
   ],
   "main": "./dist/goMain.js",
   "capabilities": {
+    "virtualWorkspaces": false,
     "untrustedWorkspaces": {
       "supported": "limited",
       "restrictedConfigurations": [