update security policy

Author: stevegrubb

SECURITY.md

@@ -5,11 +5,11 @@
 | Version | Supported          |
 | ------- | ------------------ |
 | 4.x     | :white_check_mark: |
-| 3.1.x   | :white_check_mark: |
+| 3.1.x   | :x: |
 | 3.0.x   | :x: |
-| < 3.0   | :x:                |
+| < 3.0   | :x: |
 
-Versions less than 3.0 are distribution supported.
+Versions less than 4.0 are distribution supported.
 
 ## Reporting a Vulnerability