fix md link format

MarkDaoust · tensorflower-gardener · commit 74655a96b406 · 2018-06-13T12:14:52.000-07:00
PiperOrigin-RevId: 200431906
diff --git a/SECURITY.md b/SECURITY.md
@@ -245,4 +245,4 @@ v//Fw6ZeY+HmRDFdirjD7wXtIuER4vqCryIqR6Xe9X8oJXz9L/Jhslc=
 ### Known Vulnerabilities
 
 For a list of known vulnerabilities and security advisories for TensorFlow,
-(https://github.com/tensorflow/tensorflow/blob/master/tensorflow/security/index.md)[click here].
+[click here](https://github.com/tensorflow/tensorflow/blob/master/tensorflow/security/index.md).
