changelog: add note about DHE-PSK removal

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/ChangeLog.d/9684.txt b/ChangeLog.d/9684.txt
new file mode 100644
index 0000000..115ded8
--- /dev/null
+++ b/ChangeLog.d/9684.txt
@@ -0,0 +1,2 @@
+Removals
+   * Remove support for the DHE-PSK key exchange in TLS 1.2.