changelog: Note pldm_entity_association_tree_add_entity() stabilisation

The changelog wasn't updated in 1ade87f4c6ec ("pdr : Stabilize
pldm_entity_association_tree_add_entity()"), so do that now.

Fixes: 1ade87f4c6ec ("pdr : Stabilize pldm_entity_association_tree_add_entity()")
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I0bd727f33074e66dd26bbaab7c036b3327dfadc5
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4ec395c..7bb170f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@
 
 1. pdr: Avoid ID overflow in pldm_entity_association_tree_add_entity()
 2. meson: Apply `b_ndebug=if-release` by default
+3. pdr : Stabilize pldm_entity_association_tree_add_entity()
 
 ### Removed