Merge pull request #558 from tienvx/fix-wrong-variable

docs: Fix wrong variable

README.md

@@ -224,7 +224,7 @@ Verify that all interactions took place that were registered.
 This typically should be in each test, that way the test that failed to verify is marked correctly.
 
 ```php
-$verifyResult = $verifier->verify();
+$verifyResult = $builder->verify();
 $this->assertTrue($verifyResult);
 ```