fixes link to practices in checklist
fixes link to practices in checklist

Addresses https://github.com/datacarpentry/datacarpentry.github.io/issues/400
datacarpentry/datacarpentry.github.io,ErinBecker/datacarpentry.github.io,datacarpentry/datacarpentry.github.io,ErinBecker/datacarpentry.github.io,datacarpentry/datacarpentry.github.io,ErinBecker/datacarpentry.github.io,ErinBecker/datacarpentry.github.io