Add comment about the removal of Hlt1DebugTwoTrackMVALine.

Hlt/Hlt1Conf/options/hlt1_example_throughput.py

@@ -18,6 +18,9 @@ The differences with respect to hlt1_example.py are:
 * Uses the EvtStoreSvc to handle interactions with the TES, as this is faster
   than the default HiveWhiteBoard (although doesn't work on DSTs).
 * Uses an alternative, faster IOSvc.
+* Removes the Hlt1DebugTwoTrackMVALine/debug_two_track_mva_line line, which has
+  unrealistically loose cuts and overlead from ROOT TTree I/O and should not,
+  therefore, be included in throughput tests.
 
 The latter two points may be made defaults for all HLT1 execution in the
 future, but are not currently compatible with certain input types.