Remove $compat-grid in Classic and Admin

• Type: Task
• Status: Closed
• Priority: Minor
• Resolution: Completed
• Affects Version/s: None
• Fix Version/s: Master
• Component/s: Themes Infrastructure > Compatibility Layer
• Labels: None
• Epic Link: fi-remove-bs3-bs4-compat-layer
• Sprint: S03E13 - Raleigh, S04E03 - The Queen is Dead
• Git Pull Request: https://github.com/liferay-frontend/liferay-portal/pull/499

Remove the grid portion of the BS3-BS4 compatibility layer in Classic and Admin