message: Fix typo in gradients.cc
  faciliate -> facilitate
diff: @@ -226,7 +226,7 @@ void TapeVSpace::DeleteGradient(AbstractTensorHandle* gradient) const {
  // Helper functions which delegate to `AbstractOperation`, update
  // the state of the ForwardOperation and call the tape as appropriate.
  -// These APIs are mainly to faciliate testing and are subject to change.
  +// These APIs are mainly to facilitate testing and are subject to change.
  namespace internal {
  Status Reset(AbstractOperation* op_, const char* op,
  const char* raw_device_name, ForwardOperation* forward_op_) {
  