docs: better description of ignores

[arxeiss]

Description

Improve documentation of ignores to be more descriptive.

Motivation and Context

Not clear there are global ignore rules.

Closing #3691

Types of changes

• 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 change)
• Documentation

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.