fix typo

Signed-off-by: Ian Chen <[email protected]>

src/systems/performer_detector/PerformerDetector.hh

@@ -51,7 +51,7 @@ namespace systems
   /// header will contain the key "frame_id" with a value set to the name of
   /// the model containing the PerformerDetector system and the key "state" with
   /// a value set to "1" if the performer is entering the detector's region and
-  /// "0" if the performer is leaving the region. The `datat` field of the
+  /// "0" if the performer is leaving the region. The `data` field of the
   /// header will also contain the key "count" with a value set to the
   /// number of performers currently in the region.
   ///