message: Fix typo in dart documentation
diff: @@ -16,7 +16,7 @@ documentation to build `flatc` and should be familiar with
  ## FlatBuffers Dart library code location
  -The code for the FlatBuffers Go library can be found at
  +The code for the FlatBuffers Dart library can be found at
  `flatbuffers/dart`. You can browse the library code on the [FlatBuffers
  GitHub page](https://github.com/google/flatbuffers/tree/master/dart).
  