Update shellcheck to 0.8.0

Summary:

• Feature updates and bug fixes

Full changelog available here

Test Plan:

• Ran shellcheck on a shell script shellcheck ~/packaging/common/Scripts/sync_licenses.sh
• Verified I saw expected output

Reviewers: Triage Team, JoshStrobl

Reviewed By: Triage Team, JoshStrobl

Subscribers: JoshStrobl

Differential Revision: https://dev.getsol.us/D12539