Check course for broken links and fix as needed

[Scottan]

Following #63

There may be other broken links - it worthwhile doing a check through all of the ones in the course and fixing as needed.

Broken Links Found:

• Gromacs link in https://uomresearchit.github.io/Programming-With-Python/04-software_package_management.html#searching-for-packages
• reporting guidelines link in https://uomresearchit.github.io/Programming-With-Python/CODE_OF_CONDUCT.html
• Cite me link in https://uomresearchit.github.io/Programming-With-Python/citation.html#cite-this-lesson (not necessary to fix)

[andrewgait]

This check should follow after the conda packaging chapter is moved (#61), so I am moving this to Blocked.

[andrewgait]

@Scottan @BenitoMatischen @jfecroftRSE please take a look through the course notes and note anything that looks wrong on this issue (we have #92 open already to edit the conda usage in the units chapter).

[BMatischen01]

In chapter 04, there is a link to EAFP for Python 3.6, we should link to newer versions of Python.
It looks to me like all other working links are appropriate.