clarify dropping 8.0.x

SECURITY.md

@@ -13,7 +13,7 @@ submissions, when describing the vulnerability (see https://mapserver.org/develo
 The MapServer PSC (Project Steering Committee) will release patches for security vulnerabilities 
 for the last release branch of the **two most recent release series** (such as 8.x, 7.x, 6.x, etc..., 
 where "x" is the most recent release in the series, such as: 7.6.6 being supported, but 
-not 7.6.5). 
+not 7.6.5).  For example, once 8.4 is released, support for 8.2 will be dropped. 
 Patches will only be provided **for a period of three years** from the release date of the current series.
 For example, as 8.2 has been released, now 8.2.x, and 7.6.x will be supported/patched, and 7.6.x will
 only be supported for three years from the date of the 8.0 series release (until 2025-09-12).