message: Remove unused "using" statement from arithmetic_optimizer.cc
  The only uses in the file directly refer to str_util::StringReplace
  And as absl defines the same symbol in global namespace, it causes
  "target of using declaration conflicts with declaration already in scope"
  in some cases.
diff: @@ -53,7 +53,6 @@ limitations under the License.
  #include "tensorflow/core/util/saved_tensor_slice_util.h"
  #include "tensorflow/core/util/strided_slice_op.h"
  -using tensorflow::str_util::StringReplace;
  using tensorflow::strings::StrCat;
  namespace tensorflow {
  