remove mem leak warning from debug

.changeset/rich-cars-check.md

@@ -0,0 +1,5 @@
+---
+'preact': minor
+---
+
+Remove memory leak warning from debug

debug/src/debug.js

@@ -391,13 +391,6 @@ Component.prototype.setState = function(update, callback) {
 					)}`
 			);
 		}
-	} else if (this._internal.flags & MODE_UNMOUNTING) {
-		console.warn(
-			`Can't call "this.setState" on an unmounted component. This is a no-op, ` +
-				`but it indicates a memory leak in your application. To fix, cancel all ` +
-				`subscriptions and asynchronous tasks in the componentWillUnmount method.` +
-				`\n\n${getOwnerStack(this._internal)}`
-		);
 	}
 
 	return setState.call(this, update, callback);

debug/test/browser/debug.test.js

@@ -204,29 +204,6 @@ describe('debug', () => {
 		expect(console.warn).to.not.be.called;
 	});
 
-	it('should warn when calling setState on an unmounted Component', () => {
-		let setState;
-
-		class Foo extends Component {
-			constructor(props) {
-				super(props);
-				setState = () => this.setState({ foo: true });
-			}
-			render() {
-				return <div>foo</div>;
-			}
-		}
-
-		render(<Foo />, scratch);
-		expect(console.warn).to.not.be.called;
-
-		render(null, scratch);
-
-		setState();
-		expect(console.warn).to.be.calledOnce;
-		expect(console.warn.args[0]).to.match(/no-op/);
-	});
-
 	it('should warn when calling forceUpdate inside the constructor', () => {
 		class Foo extends Component {
 			constructor(props) {