Fix APA and docutills issue

[rlanzafame]

The prior method for using APA referencing pinned docutils==0.17.1, which was causing virtual environments to not resolve in some cases (unclear why, but it had to do with low versions of sphinx being endlessly attempted).

Rather than solve dependency issues, we choose to unpin docutils, which will cause brackets [] to appear for each item on the references page. It is easier to remove these with CSS customization than.

This fix was originally created by @douden in repo https://github.com/TeachBooks/apa-test as commits TeachBooks/apa-test@704d04e and TeachBooks/apa-test@fa80dea

The fix is being implemented in this Manual (as it uses refernces) and the APA page is being updated to document and recommend the new fix.

The fix hides any span element with the class label (e.g., every <span class="label">.....</span>). We hope it doesn't cause issues elsewhere.

The fix will be released as a sphinx extension in the future, with a possible improvement on how the brackets are hidden.

[rlanzafame]

Removed static include, it is redundant to standard features: https://jupyterbook.org/en/latest/advanced/html.html#custom-css-or-javascript

also updating here: https://github.com/TeachBooks/apa-test

Ready!