Mark version 5.0.x as unsupported

Update support status for version 5.0.x to unsupported.

Author: wannaphong

SECURITY.md

@@ -4,8 +4,9 @@
 
 | Version | Supported          |
 | ------- | ------------------ |
+| 5.2.x   | :white_check_mark: |
 | 5.1.x   | :white_check_mark: |
-| 5.0.x   | :white_check_mark: |
+| 5.0.x   | :x:                |
 | 4.0.x   | :x:                |
 | 3.1.x   | :x:                |
 | 3.0.x   | :x:                |