testing: fix memory leak during unit tests (microsoft#187488)

For microsoft#187471

Author: connor4312

src/vs/workbench/api/test/browser/extHostTesting.test.ts

@@ -93,6 +93,7 @@ suite('ExtHost Testing', () => {
 
 	teardown(() => {
 		single.dispose();
+		sinon.restore();
 	});
 
 	suite('OwnedTestCollection', () => {

src/vs/workbench/contrib/debug/test/browser/callStack.test.ts

@@ -76,6 +76,10 @@ suite('Debug - CallStack', () => {
 		mockRawSession = new MockRawSession();
 	});
 
+	teardown(() => {
+		sinon.restore();
+	});
+
 	// Threads
 
 	test('threads simple', () => {