Grammar fix 6.3.18 Use of Qualitative Severity Rating

[sonnyvanlingen]

Currently:

This covers all items in metrics regardless of their origin. Even though the Qualitative Severity Rating is a specified property, **it's** usage is discouraged as it provides no information about the assessment inputs.

Fix:

This covers all items in metrics regardless of their origin. Even though the Qualitative Severity Rating is a specified property, **its** usage is discouraged as it provides no information about the assessment inputs.

Announced:
https://groups.oasis-open.org/discussion/new-issue-grammar-fix-6318-use-of-qualitative-severity-rating