Go-github: Remove some fields of IssueListCommentsOptions

[you06]

Sort and Direction not work since GitHub changed its API.

https://developer.github.com/v3/repos/commits/#list-commits

https://github.com/google/go-github/blob/e881974953e6ab6d1a6a1610e98ed6401a3aa1ba/github/issues_comments.go#L37-L48

[gmlewis]

Thank you, @you06 !
The Sort and Direction fields need to be removed. Although these apparently no longer are supported, this change is still a breaking API change, so I will mark it that way.

This would be a great PR for any new contributor to this repo or a new Go developer.
All contributions are greatly appreciated!

Feel free to volunteer for any issue and the issue can be assigned to you so that others don't attempt to duplicate the work.

Please check out our CONTRIBUTING.md guide to get started.

Thank you!

[juanri0s]

I can work on this! 😁

[gmlewis]

Thank you, @juanri0s ! It is yours.

[juanri0s]

@gmlewis I have removed the fields from the struct and the fields in the tests as well. Are we expecting this change in any other area other than issues_comments.go? Or do I need to go through the GH API docs and check myself?

[gmlewis]

These fields were identified in the issue. You are welcome to look through the docs for other discrepancies.