MAINT: PEP8 further compliance (manual check) constants.py module

[alan-techdev]

This partially fixes the Issue 3231 by focusing on none public API inside the pypdf/constants.py module.
public API for constants module

In regards to constants.py line 586 ( op = "/op") and 602 (ca = "/ca"); they are being left in order to avoid breaking the test cases (test_constants.py::test_slash_prefix) line 36 which state the below

 if cls == GraphicsStateParameters and attr in ["ca", "op"]:
                continue

The attribute is hardcoded so either we change the test case or ?
The reason is to keep PR into minium

[codecov]

Codecov Report

❌ Patch coverage is 96.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 97.59%. Comparing base (64a793b) to head (b9e6b9f).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pypdf/_page.py	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3750   +/-   ##
=======================================
  Coverage   97.59%   97.59%           
=======================================
  Files          55       55           
  Lines       10228    10228           
  Branches     1877     1877           
=======================================
  Hits         9982     9982           
  Misses        141      141           
  Partials      105      105           

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[stefan6419846]

Could you please have a look at the failing tests?

Additionally, this unfortunately is wrong - pypdf.constants is a public module, thus - even if they are not part of the docs directly - they have to be considered public API. Renaming them thus requires a proper deprecation process.

[alan-techdev]

Noted. I will try to address private module instead