doc: security: Update doc to have latest info; fix a typo

Signed-off-by: Siddharth Chandrasekaran <[email protected]>

SECURITY.md

@@ -2,15 +2,18 @@
 
 ## Supported Versions
 
-LibOSDP will support the last 2 [releases](https://github.com/goToMain/libosdp/releases) for security and and bug fixes.
+LibOSDP will support the last 2 [releases][1] for security and and bug fixes.
 
-| Version | Supported          |
-| ------- | ------------------ |
-| <= 1.5  | :x:                |
-| 2.0.x   | :white_check_mark: |
-| 2.1.x   | :white_check_mark: |
-| master  | :white_check_mark: |
+| Version | Branch | Supported          |
+| ------- | -------|------------------- |
+| <= 1.5  | N/A    | :x:                |
+| 2.4.x   | 2.4.x  | :white_check_mark: |
+| latest  | master | :white_check_mark: |
 
 ## Reporting a Vulnerability
 
-Please end an email to Siddharth Chandrasekaran <[email protected]> ([GPG](https://github.com/sidcha.gpg))
+Please send an email to Siddharth Chandrasekaran <[email protected]>
+([GPG]([2])).
+
+[1]: https://github.com/goToMain/libosdp/releases
+[2]: https://github.com/sidcha.gpg