Update SECURITY.md (#16992)

Author: justinengland

SECURITY.md

@@ -9,7 +9,11 @@ currently being supported with security updates.
 | 1.3.x   | :x:                |
 | 1.4.x   | :x:                |
 | 1.5.x   | :x:                |
-| 1.6.x   | :white_check_mark: |
+| 1.6.x   | :x:                |
+| 1.7.x   | :x:                |
+| 1.8.x   | :x:                |
+| 2.0.x   | :x:                |
+| 2.1.x   | :white_check_mark: |
 
 ## Reporting a Vulnerability