message: remove FixedSchedule parameter from example XML
diff: <io name="writer">
  <engine type="InSituMPI">
  <parameter key="verbose" value="5"/>
  - <parameter key="FixedSchedule" value="true"/>
  </engine>
  </io>
  <io name="reader">
  <engine type="InSituMPI">
  <parameter key="verbose" value="5"/>
  - <parameter key="FixedSchedule" value="true"/>
  </engine>
  </io>
  </adios-config>
  