add note do updating text

_source/index.rst

@@ -77,6 +77,9 @@ change ``/home/maarten/my-passwords.yml`` to a more sensible location...
    been included. There will be *no* mention of this in the error, however... It
    will just fail at a step that runs ``manage.py``.
 
+.. note:: If you update the configuration repo (`/edx/bin/update configuration 
+  <branch>`), this will most likely update the update script, so your changes 
+  will be gone again.
 
 Adding Let's Encrypt TLS certificates
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