Move DocCommentLineLength Sniff to Docs ruleset

[jaymcp]

Description

To aid test discovery, the Docs ruleset has been renamed from 'BigBite-Docs' to 'BigBiteDocs'.
As a consequence, the BigBite.Commenting.DocCommentLineLength Sniff code is now BigBiteDocs.Commenting.DocCommentLineLength.

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.