Update Packaging-Gooey.md

[redmond2742]

pathex should just be the path, on the actual python file. Tried to make this more clear with this edit.

Hello there!

Make sure you've followed the Contributing guidelines before finalizing your pull request.

TL;DR:

• [ X] You're opening this PR against the current release branch
• [ X] Works on both Python 2.7 & Python 3.x
• [X ] Commits have been squashed and includes the relevant issue number
• [ X] Pull request description contains link to relevant issue or detailed notes on changes
• [ X] This must include example code demonstrating your feature or the bug being fixed
• [ X] All existing tests pass
• [X ] Your bug fix / feature has associated test coverage
• [X ] README.md is updated (if relevant)