software/rapid-cdn: Remove useless update-command

The rapid-cdn software.cfg manually downloads/copies a setup.py and
a software.py into a folder and then installs it as a develop egg.

Installing a develop-egg creates a .egg-info or a .dist-info into
the source folder.

In rapid-cdn/software.cfg an update-command resulted in the folder
being deleted and recreated on every update for no gain. This also
deleted the .egg-info or .dist-info, breaking the develop egg
installation.

With the zc.buildout 3.0.1+slapos003 release, zc.recipe.egg:develop
is now able to detect such cases and trigger the reinstallation of
the .egg-info or .dist-info. Still, this update-command remains the
cause of useless computations.

software/rapid-cdn/software.cfg

@@ -38,7 +38,6 @@ url = ${:_profile_base_location_}/software.py
 recipe = plone.recipe.command
 stop-on-error = True
 location = ${buildout:parts-directory}/${:_buildout_section_name_}
-update-command = ${:command}
 command =
   rm -fr ${:location} &&
   mkdir -p ${:location} &&