Update is neede regarding distinct_()

[windysky]

Warning message:
distinct_() was deprecated in dplyr 0.7.0.
ℹ Please use distinct() instead.
ℹ See vignette('programming') for more help
ℹ The deprecated feature was likely used in the richR package.
Please report the issue to the authors.
This warning is displayed once every 8 hours.
Call lifecycle::last_lifecycle_warnings() to see where this warning was generated.

[guokai8]

@windysky Done!