DOC: Small fix ups for modernized size

[bashtage]

Some small tweaks to catch missed elements

• code/documentation is well formatted.
• properly formatted commit message. See
  NumPy's guide.

Notes:

• It is essential that you add a test when making code changes. Tests are not
  needed for doc changes.
• When adding a new function, test values should usually be verified in another package (e.g., R/SAS/Stata).
• When fixing a bug, you must add a test that would produce the bug in master and
  then show that it is fixed with the new code.
• New code additions must be well formatted. Changes should pass flake8. If on Linux or OSX, you can
  verify you changes are well formatted by running

  git diff upstream/master -u -- "*.py" | flake8 --diff --isolated
  

  assuming flake8 is installed. This command is also available on Windows
  using the Windows System for Linux once flake8 is installed in the
  local Linux environment. While passing this test is not required, it is good practice and it help
  improve code quality in statsmodels.
• Docstring additions must render correctly, including escapes and LaTeX.

[codecov]

Codecov Report

Merging #6052 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #6052   +/-   ##
=======================================
  Coverage   83.57%   83.57%           
=======================================
  Files         607      607           
  Lines       96404    96404           
  Branches    10471    10471           
=======================================
  Hits        80565    80565           
  Misses      13458    13458           
  Partials     2381     2381

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[coveralls]

Coverage remained the same at 86.04% when pulling 89d5c29 on bashtage:css-fix into 60f7a2b on statsmodels:master.