Double-free goes under security, not bugfix.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/ChangeLog.d/fix-session-copy-bug.txt b/ChangeLog.d/fix-session-copy-bug.txt
index 46e3d8e..6286fa8 100644
--- a/ChangeLog.d/fix-session-copy-bug.txt
+++ b/ChangeLog.d/fix-session-copy-bug.txt
@@ -1,4 +1,4 @@
-Bugfix
+Security
    * Fix a double-free that happened after mbedtls_ssl_set_session() or
      mbedtls_ssl_get_session() failed with MBEDTLS_ERR_SSL_ALLOC_FAILED
      (out of memory). After that, calling mbedtls_ssl_session_free()