Remove changes/bug7129
Our convention is that we use the changelog to note release-to-release
changes; we don't need to add changelog entries for bugs that didn't
appear in any released version of Tor. (By convention, we sometimes
say "this bug does not appear in any released version of Tor" or words
to that effect in the commit message so that when Roger goes to make
sure the changelog is right, he knows not to expect a changelog entry
for that part.)