message: Update custom_operators.md
  Documentation issue
diff: @@ -137,7 +137,7 @@ operations instead of a single operator.
  ## Special TF Graph Attributes
  -When Toco convertes a TF graph into TFLite format, it makes some assumption
  +When Toco converts a TF graph into TFLite format, it makes some assumption
  about custom operations that might be not correct. In this case, the generated
  graph can be not executable.
  