Update bug-12393b.php

Author: staabm

tests/PHPStan/Analyser/nsrt/bug-12393b.php

@@ -144,7 +144,7 @@ public function getMixed()
 
 }
 
-class Foo
+class FooStringInt
 {
 
 	public int $foo;
@@ -195,6 +195,8 @@ public function doBar(): void
 	{
 		$this->foo = true;
 		assertType('string', $this->foo);
+		$this->foo = false;
+		assertType('string', $this->foo);
 	}
 }