Drop pypy3-dev (#1700)
Drop pypy3-dev (#1700)

PyPy has now only one development tip, `default`,
others are version-line-specific maintenance branches.
The py3k branch has been closed in 2016.
As such, a separate pypy3-dev entry no longer makes sense.
sebhahn/pyenv,yyuu/pyenv,yyuu/pyenv,pyenv/pyenv,sebhahn/pyenv,pyenv/pyenv,pyenv/pyenv,sebhahn/pyenv