Remove myself from packages I cannot maintain

When adding these packages to testing, I did think I would use them. Turns out I didn't. Meanwhile, I didn't have time to maintain the packages and silently ignored all emails. I'm sorry! Back in the day, I did not know that testing packages do not need a maintainer, which is why I added myself as maintainer.

The last package I am listed as maintainer is extremely low maintenance, and I still use it, which very much increases the likelihood of me having time to review PRs.

@fluix Are you fine with being the maintainer of py3-starlette?