bugfix: InsertDataset.WithDialect return old dataset

[chen56]

bugfix: InsertDataset.WithDialect return old dataset, should be return new dataset

[codecov]

Codecov Report

Merging #126 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #126   +/-   ##
=======================================
  Coverage   87.45%   87.45%           
=======================================
  Files          47       47           
  Lines        3556     3556           
=======================================
  Hits         3110     3110           
  Misses        386      386           
  Partials       60       60

Impacted Files	Coverage Δ
insert_dataset.go	97.4% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3237124...cf5f782. Read the comment docs.

[doug-martin]

Thank you for the pr I'm currently out of town and won't be able to get this merged until the weekend. Sorry for the delay.