releases: clarify supported and outdated releases

(From yocto-docs rev: c3d6c36497f7af1ca19357c5474ff1e5743f597b)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Reported-by: Quentin Schulz <foss@0leil.net>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/releases.rst

@@ -1,8 +1,8 @@
 .. SPDX-License-Identifier: CC-BY-SA-2.0-UK
 
-=========================
- Current Release Manuals
-=========================
+===========================
+ Supported Release Manuals
+===========================
 
 *******************************
 3.3 'hardknott' Release Series
@@ -36,7 +36,7 @@
 - :yocto_docs:`3.1.8 Documentation </3.1.8>`
 
 ==========================
- Previous Release Manuals
+ Outdated Release Manuals
 ==========================
 
 *************************