.vscode/launch.json: unset test guard env var

Bug (microsoft/vscode#83187) is causing VSCODE_GO_IN_TEST env var
to leak and subsequent extension tests to fail to activate fully.
This is a short-term workaround until we find a better solution
to deactivate the extension during testing or learn how to test
a bundled extension better (microsoft/vscode-extension-samples#363).

Change-Id: If5b9b56ef8360547c518240a42286c9385b53b44
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/270802
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Suzy Mueller <suzmue@golang.org>
diff --git a/.vscode/launch.json b/.vscode/launch.json
index 475ef8c..e7e3d55 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -18,6 +18,9 @@
 			"sourceMaps": true,
 			"smartStep": true,
 			"preLaunchTask": "npm: webpack",
+			"env": {
+				"VSCODE_GO_IN_TEST": ""  // Enable code
+			},
 		},
 		{
 			"name": "Launch as server",