engine/install: add Ubuntu 23.10 EOL date

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah

content/engine/install/ubuntu.md

@@ -39,7 +39,7 @@ To install Docker Engine, you need the 64-bit version of one of these Ubuntu
 versions:
 
 - Ubuntu Noble 24.04 (LTS)
-- Ubuntu Mantic 23.10
+- Ubuntu Mantic 23.10 (EOL: [July 12, 2024](https://wiki.ubuntu.com/Releases))
 - Ubuntu Jammy 22.04 (LTS)
 - Ubuntu Focal 20.04 (LTS)