Update changelog to cover #4720

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>

ChangeLog

diff --git a/ChangeLog b/ChangeLog
index 5074249..019e8fa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -58,7 +58,7 @@
    * Remove the MBEDTLS_TEST_NULL_ENTROPY config option. Fixes #4388.
    * The interface of the GCM module has changed to remove restrictions on
      how the input to multipart operations is broken down. mbedtls_gcm_finish()
-     now takes an extra output parameter for the last partial output block.
+     now takes extra output parameters for the last partial output block.
      mbedtls_gcm_update() now takes extra parameters for the output length.
      The software implementation always produces the full output at each
      call to mbedtls_gcm_update(), but alternative implementations activated