Fix docstrings being rendered incorrectly in API documentation

[jaladh-singhal]

Some of the docstrings in tardis API documentation are being rendered incorrectly as in tardis.util.base where parameter name and type appears to be merged in html (e.g. atomic_numberint), despite it is separated by colon in docstrings (atomic_number: int).

Also there's some problem in latex equation in intensity_black_body due to which it is getting line-breaked in html.

Some Pointers

• It might have something to do with sphinx config.py file or rtd-theme settings
• Find out all other submodules or modules which have such or related problems and fix them.

[jaladh-singhal]

@arjunsavel regarding the 1st part where parameter name and type gets merged - that was due to some CSS bug as mentioned in numpydoc#215 and has been fixed by latest update of sphinx_rtd_theme to 0.5.0 (released 8-9 hrs ago on conda-forge) - I've tested this locally for my widgets module api docs and it works.

Since we have sphinx_rtd_theme unpinned - it should work next time docs-pipeline builds docs (or if you've rights you can manually trigger the pipeline to see it now).

But for 2nd part about latex equation - the equation is still line-breaked with this update, so most probably it is a latex error IMO.