Remove PY2 encoding declaration

[dorothykiz1]

We are trying to drop any python 2 related syntaxes, comments, or code and replace this with python 3 equivalent code.

Most files in the asv directory have the first-line comment on top of the file # -*- coding: utf-8 -*-

The idea is to remove this line from all files as this encoding declaration is related to python 2

[LucyJimenez]

As example you can see the PR: https://github.com/airspeed-velocity/asv/pull/1048/files

[Tushcathy]

#take

[datapythonista]

Same here, looks like all them are now gone. Thanks a lot @Tushcathy and @mariamadronah