devel/py-robotframework-selenium2library: Rename to match upstream

The Python package was forked from the old SeleniumLibrary as
Selenium2Library to use Selenium 2 and WebDriver technologies.

Later then it was renamed back to its original name, SeleniumLibrary.

Thus rename the existing port to py-robotframework-seleniumlibrary and
update the pkg-descr to reflect the new constellation.

PR: 224814
Submitted by: vladimir.chukharev@gmail.com (maintainer)
Reviewed by: miwi (earlier version)