Minor documentation rendering improvements

[kandersolar]

• [ ] Closes #xxxx
• I am familiar with the contributing guidelines
• [ ] Tests added
• [ ] Updates entries in docs/sphinx/source/reference for API changes.
• [ ] Adds description and name entries in the appropriate "what's new" file in docs/sphinx/source/whatsnew for all changes. Includes link to the GitHub Issue with :issue:`num` or this Pull Request with :pull:`num`. Includes contributor name and/or GitHub username (link with :ghuser:`user`).
• [ ] New code is fully documented. Includes numpydoc compliant docstrings, examples, and comments where necessary.
• Pull request is nearly complete and ready for detailed review.
• Maintainer: Appropriate GitHub Labels (including remote-data) and Milestone are assigned to the Pull Request and linked Issue.

This PR fixes a handful of instances like this, where a bulleted list is rendered with quotation formatting:

After fixing the indentation, it renders better:

It also improves the rendering of a couple of equations I noticed along the way.

Here is a table of the changed docstrings:

Function	Stable	PR
pvlib.irradiance.reindl	link	link
pvlib.irradiance.erbs	link	link
pvlib.irradiance.erbs_driesse	link	link
pvlib.irradiance.orgill_hollands	link	link
pvlib.irradiance.boland	link	link
pvlib.irradiance.gti_dirint	link	link
pvlib.irradiance.louche	link	link
pvlib.iam.marion_diffuse	link	link
pvlib.iam.marion_integrate	link	link
pvlib.iam.convert	link	link
pvlib.iam.fit	link	link
pvlib.pvsystem.sapm_effective_irradiance	link	link
pvlib.pvsystem.singlediode	link	link
pvlib.spectrum.spectrl2	link	link
pvlib.spectrum.spectral_factor_firstsolar	link	link