Update line length sniff to disregard lines containing specific prefixes

[jaymcp]

Description

The BigBite.Commenting.DocCommentLineLength Sniff didn't correctly account for comment lines that start with specific prefixes.
It skipped scanning WP plugin/theme comments completely, where really it should only skip checking the Description: line, as that is the most likely to be excessively long.

Types of changes (if applicable):

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).

Checklist (if applicable):

• All checks pass when running `composer run all-checks.