Fix broken Appendix links due to section overhaul

[govi20]

No description provided.

[snicoll]

@govi20 Thank you very much for picking up a first-timers-only issue and then making your first contribution to Spring Boot. The proposed changes have been merged into master with a polish commit.

I suggest to reset master on your fork (make sure you don't have changes of your own first) as you need to start any further PR from a clean slate:

git checkout master
git fetch upstream
git reset upstream/master --hard

Make sure to update master on your fork before creating a branch for your next PR. This will avoid the merge commits you had to deal with in this one. Hope that helps.