fix histogram indent in exampleConfig.js

exampleConfig.js

@@ -72,7 +72,7 @@ Optional Variables:
   repeaterProtocol: whether to use udp4 or udp6 for repeaters.
                     ["udp4" or "udp6", default: "udp4"]
 
-    histogram:      for timers, an array of mappings of strings (to match metrics) and
+  histogram:        for timers, an array of mappings of strings (to match metrics) and
                     corresponding ordered non-inclusive upper limits of bins.
                     For all matching metrics, histograms are maintained over
                     time by writing the frequencies for all bins.