Fix missing category in CHANGES

Backport-of: 6920a1ee72644f452ff04e506cb03dd610b41c40
diff --git a/CHANGES.md b/CHANGES.md
index f3c62f1..912e93f 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -3,6 +3,8 @@
 
 ## RJ 4.4.0 ~ StatET 4.4.0
 
+### RServi Pool
+
   * The enum of pool node states (`PoolNodeState`) has the additional state DISPOSING for nodes
     marked for disposal but not yet DISPOSED. (Bug 572191)