message: Fix invalid link in security advisories page
  The link in security advisories page was invalid,
  should be `[SECURITY.md](https://...)` instead
  of `(https://...)[SECURITY.md]`. This fix correct
  the link issue.
diff: @@ -4,7 +4,7 @@ We regularly publish security advisories about using TensorFlow.
  *Note*: In conjunction with these security advisories, we strongly encourage
  TensorFlow users to read and understand TensorFlow's security model as outlined
  -in (https://github.com/tensorflow/tensorflow/blob/master/SECURITY.md)[SECURITY.md].
  +in [SECURITY.md](https://github.com/tensorflow/tensorflow/blob/master/SECURITY.md).
  | Advisory Number | Type | Versions affected | Reported by | Additional Information |
  |-----------------|--------------------|:-----------------:|-----------------------|-----------------------------|
  