src/goMain: change gopls_gc_details to gopls.gc_details

golang.org/cl/263057 changed the command prefix to 'gopls.'.

Change-Id: If5eee2e991a6c1ef0a5efbc04feeab7fc06b3ce6
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/263900
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Trust: Peter Weinberger <pjw@google.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Peter Weinberger <pjw@google.com>

src/goMain.ts

@@ -464,7 +464,7 @@ export function activate(ctx: vscode.ExtensionContext) {
 		}
 		vscode.commands.executeCommand('gc_details', doc)
 			.then(undefined, (reason0) => {
-				vscode.commands.executeCommand('gopls_gc_details', doc)
+				vscode.commands.executeCommand('gopls.gc_details', doc)
 					.then(undefined, (reason1) => {
 						vscode.window.showErrorMessage(`"Go: Toggle gc details" command failed: gc_details:${reason0} gopls_gc_details:${reason1}`);
 					});