docs(changelog): changelog for lts-v2.8.15 release

Generated with the command:
npm run release -- --release-as 2.8.15

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: Ibb920e90a6f44a858b9f4709dbeb22e22ab86e78
diff --git a/pyproject.toml b/pyproject.toml
index bd93177..608c912 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "trusted-firmware-a"
-version = "2.8.14"
+version = "2.8.15"
 description = "Trusted Firmware-A (TF-A) Python dependencies."
 authors = ["Arm Ltd."]
 license = "BSD-3-Clause"