extension/src: cleanup extension api

Removes properties from the extension API because those properties were
a hallucination - they were never populated.

Fixes #3574

Change-Id: I53ef2bc93e02f884e4d25b657edc83d0339135c0
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/621497
kokoro-CI: kokoro <[email protected]>
Reviewed-by: Hongxiang Jiang <[email protected]>
Reviewed-by: Hyang-Ah Hana Kim <[email protected]>
Commit-Queue: Hyang-Ah Hana Kim <[email protected]>
Commit-Queue: Ethan Reesor <[email protected]>

Author: firelizzard18

extension/src/export.d.ts

@@ -8,9 +8,6 @@ export { ToolAtVersion } from './goTools';
 
 export interface CommandInvocation {
 	binPath: string;
-	args?: string[] | string;
-	env?: Object;
-	cwd?: string;
 }
 
 export interface ExtensionAPI {