[core] Update security.md (#45839)

Author: DiegoAndai

SECURITY.md

@@ -6,7 +6,8 @@ The versions of the project that are currently supported with security updates.
 
 | Material UI version | Release    | Supported                            |
 | ------------------: | :--------- | :----------------------------------- |
-|              ^6.0.0 | 2024-08-26 | :white_check_mark: Stable major      |
+|              ^7.0.0 | 2025-03-26 | :white_check_mark: Stable major      |
+|              ^6.0.0 | 2024-08-26 | :white_check_mark: Long-term support |
 |              ^5.0.0 | 2021-09-16 | :white_check_mark: Long-term support |
 |              ^4.0.0 | 2019-06-23 | :x:                                  |
 |              ^3.0.0 | 2018-08-27 | :x:                                  |