Søren Bredlund Caspersen authored Nov 30, 2020 and freetrader committed Nov 30, 2020

Numbering was broken, starting over again and again, instead of going from 1 to 9.
This should make the ordered list in `CONTRIBUTING.md` render correctly with `mkdocs`.

Test plan
---------

Make sure you have `mkdocs` and `mkdocs-material` installed (`pip install mkdocs` and `pip install mkdocs-material` - adjust per your installation / distribution)

Go to your working area root folder, and run the doc deployment prep commands from `.gitlab-ci.yml`:

```
mkdir files-for-mkdocs
(cd files-for-mkdocs ; ln -s ../* . ; rm -rf files-for-mkdocs)
rm -f files-for-mkdocs/{depends,src}
tar cf - $(find src depends -name \*.md) | ( cd files-for-mkdocs ; tar xf - )
tar cf - src/chainparams.cpp src/crypto/sha256_sse4.cpp src/interfaces/*.h src/qt/intro.cpp src/univalue/COPYING | ( cd files-for-mkdocs ; tar xf - )
rm -f files-for-mkdocs/doc/release-notes.md
mkdocs build
```

Then run `mkdocs serve` and browse to http://127.0.0.1:8000
to take a look at the rendered document (and compare to previous
version using the same doc building procedure on `master` before this change)