Restore the Global enableRainbow after the write test

The leaked value made any rerun against the same profile fail the
preview suite, which forced every local run to start from a wiped
user-data directory.

Author: ShortArrow

src/test/suite/extension.test.ts

@@ -13,6 +13,10 @@ const extensionName = "LineNumberDeco";
 suite('Extension Test Suite', () => {
 	vscode.window.showInformationMessage('Start all tests.');
 
+	suiteTeardown(async () => {
+		await vscode.workspace.getConfiguration(extensionName).update('enableRainbow', undefined, vsCodeGlobal);
+	});
+
 	test('Sample test', () => {
 		assert.strictEqual(-1, [1, 2, 3].indexOf(5));
 		assert.strictEqual(-1, [1, 2, 3].indexOf(0));