Correct inaccurate comment

The description of the "Side" channel index for the tracker was wrong

Tracker/TrackerDetDescr/TrackerIdDictFiles/data/IdDictTracker.xml

@@ -33,8 +33,9 @@
   </field>
 
   <field name="side">
-    <label name="Upstream"    value="0" />
-    <label name="Downstream"  value="1" />
+  <!-- The "upper" side is the side with the pigtail -->
+    <label name="Upper"    value="0" />
+    <label name="Lower"    value="1" />
   </field>
 
   <region>
@@ -43,7 +44,7 @@
     <range field="layer"      values="Upstream Central Downstream" />
     <range field="phi_module" values="Bottom LowerMiddle UpperMiddle Top" wraparound="FALSE" />
     <range field="eta_module" values="Starboard Port" wraparound="FALSE" />
-    <range field="side"       values="Upstream Downstream" />
+    <range field="side"       values="Upper Lower" />
     <range field="strip"      minvalue="0" maxvalue="767" />
   </region>