Update security policy for 0.9.68 release

Additional fixes:
Ubuntu 16.04 ais EOL. This means that Firejail 0.9.38 is (to
reasonable knowledge) not supported by any mainstream distros.

Ubuntu 21.04 is also EOL.

SECURITY.md

@@ -4,8 +4,9 @@
 
 | Version | Supported by us | EOL | Supported by distribution |
 | ------- | ------------------ | ------------------ | --------------------------------------------------------------------------------- |
-| 0.9.66 | :heavy_check_mark: | | :white_check_mark: Debian 11 **backports**, Debian 12 (testing/unstable) |
-| 0.9.64 | :x: | | :white_check_mark: Debian 10 **backports**, Debian 11, Ubuntu 21.04, Ubuntu 21.10 |
+| 0.9.68 | :heavy_check_mark: | | |
+| 0.9.66 | :x: | | :white_check_mark: Debian 11 **backports**, Debian 12 (testing/unstable) |
+| 0.9.64 | :x: | | :white_check_mark: Debian 10 **backports**, Debian 11, Ubuntu 21.10 |
 | 0.9.62 | :x: | | :white_check_mark: Ubuntu 20.04 LTS, Ubuntu 20.10 |
 | 0.9.60 | :x: | 29 Dec 2019 | |
 | 0.9.58 | :x: | | :white_check_mark: Debian 9 **backports**, Debian 10 |
@@ -18,7 +19,7 @@
 | 0.9.44 | :x: | | :white_check_mark: Debian 9 |
 | 0.9.42 | :x: | 22 Oct 2016 | |
 | 0.9.40 | :x: | 09 Sep 2016 | |
-| 0.9.38 | :x: |   | :white_check_mark: Ubuntu 16.04 LTS |
+| 0.9.38 | :x: | 31 May 2016 |   |
 | <0.9.38 | :x: | Before 05 Feb 2016 | |
 
 ## Security vulnerabilities