yafc: Fix test server

[rfinnie]

speedtest.tele2.net hasn't been working for a long time. Replace
with ftp.gnu.org which is the least likely to go away anytime soon
(though I wouldn't trust any FTP server staying around these days)

• Have you followed the guidelines for contributing?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing brew install <formula>)?

---

[SMillerDev]

Maybe we can just download a file from formulae.brew.sh instead? If that goes away we can fix it ourselves.

[rfinnie]

Maybe we can just download a file from formulae.brew.sh instead? If that goes away we can fix it ourselves.

formulae.brew.sh does not appear to be an FTP server?