Style fix

Add space in the ChangeLog.
diff --git a/ChangeLog b/ChangeLog
index b50d223..2ebde98 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,7 +4,7 @@
 
 Bugfix
     * Fix failure in hmac_drbg in the benchmark sample application, when
-     MBEDTLS_THREADING_C is defined. Found by TrinityTonic, #1095
+      MBEDTLS_THREADING_C is defined. Found by TrinityTonic, #1095
 
 = mbed TLS 2.1.14 branch released 2018-07-25