Adds ChangeLog entry

Commit adds ChangeLog entry for removal of
MBEDTLS_SSL_TRUNCATED_HMAC.

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/ChangeLog.d/rm-truncated-hmac-ext.txt b/ChangeLog.d/rm-truncated-hmac-ext.txt
new file mode 100644
index 0000000..e3391f8
--- /dev/null
+++ b/ChangeLog.d/rm-truncated-hmac-ext.txt
@@ -0,0 +1,3 @@
+Removals
+   * Remove MBEDTLS_SSL_TRUNCATED_HMAC config option since it is no longer
+     supported in 3.0. Addresses #4341.