doc: touchup release notes for 2.3

- At the top of the release notes, we announce sandboxing is now enabled by default,
then at the bottom it says it's now disabled when missing kernel support. These
can be merged into one point for clarity.

- The point about `max-jobs` defaulting to 1 appears unrelated to sandboxing.

doc/manual/release-notes/rl-2.3.xml

@@ -33,9 +33,13 @@ incompatible changes:</para>
   </listitem>
 
   <listitem>
-    <para>The installer now enables sandboxing by default on
+    <para>The installer now enables sandboxing by default on Linux when the
-    Linux. The <literal>max-jobs</literal> setting now defaults to
+    system has the necessary kernel support.
-    1.</para>
+    </para>
+  </listitem>
+
+  <listitem>
+    <para>The <literal>max-jobs</literal> setting now defaults to 1.</para>
   </listitem>
 
   <listitem>
@@ -82,11 +86,6 @@ incompatible changes:</para>
     the duration of Nix function calls to stderr.</para>
   </listitem>
 
-  <listitem>
-    <para>On Linux, sandboxing is now disabled by default on systems
-    that don’t have the necessary kernel support.</para>
-  </listitem>
-
 </itemizedlist>
 
 </section>