Fix Changelog entry for #1533 fix as a Change not a bugfix

ChangeLog

diff --git a/ChangeLog b/ChangeLog
index 89a9469..9ea55e1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -5,8 +5,6 @@
 Bugfix
    * Fix compilation error on C++, because of a variable named new.
      Found and fixed by Hirotaka Niisato in #1783.
-   * Change the shebang line in Perl scripts to look up perl in the PATH.
-     Contributed by fbrosson in #1533.
    * Fix a memory leak in mbedtls_x509_csr_parse(), found by catenacyber,
      Philippe Antoine. Fixes #1623.
    * Clarify documentation for mbedtls_ssl_write() to include 0 as a valid
@@ -18,6 +16,10 @@
    * Fix compilation error when MBEDTLS_ARC4_C is disabled and
      MBEDTLS_CIPHER_NULL_CIPHER is enabled. Found by TrinityTonic in #1719.
 
+Changes
+   * Change the shebang line in Perl scripts to look up perl in the PATH.
+     Contributed by fbrosson in #1533.
+
 = mbed TLS 2.7.4 branch released 2018-06-18
 
 Bugfix