use unit example in NXmonochromator

Author: lukaspie

base_classes/NXmonochromator.nxdl.xml

@@ -60,9 +60,9 @@
     <field name="energy_errors" type="NX_FLOAT" units="NX_ENERGY">
         <doc>energy standard deviation</doc>
     </field>
-    <field name="energy_dispersion" type="NX_FLOAT" units="NX_ANY">
+    <field name="energy_dispersion" type="NX_FLOAT" units="eV/mm">
         <doc>
-             Energy dispersion at the exit slit, typically given as eV/mm.
+             Energy dispersion at the exit slit.
         </doc>
     </field>
     <field name="wavelength_dispersion" type="NX_FLOAT" units="NX_ANY">