Remove my personal nickserv creds from example.conf.

To anyone thinking of getting clever with those credentials: no, of course I
changed them. Try harder. However, you can learn from my mistake.

I checked those credentials in by copying my testing config to example.conf,
thinking "I know, I'll fix the login before committing", and then forgetting.
Lesson: fix them _immediately_, before `git-add` sees them, or you might never
remember.
Remove personal info from example.conf.

The info that was present has been invalidated, so it's no longer unsafe, but
the example should still be general.