nixos/doc: add release note for Qt 5.1{2,4} deprecation

nixos/doc/manual/from_md/release-notes/rl-2305.section.xml

@@ -88,6 +88,15 @@
           relying on this should provide their own implementation.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          Qt 5.12 and 5.14 have been removed, as the corresponding
+          branches have been EOL upstream for a long time. This affected
+          under 10 packages in nixpkgs, largely unmaintained upstream as
+          well, however, out-of-tree package expressions may need to be
+          updated manually.
+        </para>
+      </listitem>
       <listitem>
         <para>
           The <literal>nix.readOnlyStore</literal> option has been

nixos/doc/manual/release-notes/rl-2305.section.md

@@ -31,6 +31,8 @@ In addition to numerous new and upgraded packages, this release has the followin
 
 - The EC2 image module previously detected and activated swap-formatted instance store devices and partitions in stage-1 (initramfs). This behaviour has been removed. Users relying on this should provide their own implementation.
 
+- Qt 5.12 and 5.14 have been removed, as the corresponding branches have been EOL upstream for a long time. This affected under 10 packages in nixpkgs, largely unmaintained upstream as well, however, out-of-tree package expressions may need to be updated manually.
+
 - The `nix.readOnlyStore` option has been renamed to `boot.readOnlyNixStore` to clarify that it configures the NixOS boot process, not the Nix daemon.
 
 ## Other Notable Changes {#sec-release-23.05-notable-changes}