doc: remove unused/duplicated reference links
Summary
I noticed some un-styled markdown at https://github.com/nodejs/node/pull/12756, and the original PR may take more time. To avoid more conflicts and make the diff a bit small, it would be nice if we can take the docs fix commits from it. Then I removed the unused/duplicated reference links.
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines
Affected core subsystem(s)
doc