Cleanup: remove "<pep8 compliant>" from headers

It can be assumed that all scripts comply with basic pep8 formatting
regarding white-space, indentation etc.

Also remove note in best practices page & update `tests/python/pep8.py`.

If we want to exclude some scripts from make format,
this can be done by adding them to `ignore_files` in:
source/tools/utils_maintenance/autopep8_format_paths.py

Or using `# nopep8` for to ignore for individual lines.

Ref T98554

release/scripts/modules/bl_console_utils/autocomplete/intellisense.py

@@ -2,8 +2,6 @@
 
 # Copyright (c) 2009 www.stani.be
 
-# <pep8-80 compliant>
-
 """This module provides intellisense features such as:
 
 * autocompletion