user name to username

[evinugur]

Naming conventions should be consistent across reddit
‘username’ seems to be the way to go

[bsimpson63]

Thanks, but we don't accept pull requests like these because purely cosmetic updates make it difficult to follow the commit history.

[evinugur]

Ah, ok. A lot of the files I touched were doc strings anyway, but I think at least this specific string should be merged in because it's actually viewable to users of the site and is a small diff on one file as opposed to the handful I proposed to be merged for the PR