Set calibration visualizer image channel correctly

This makes the calibration visualizer take in a channel name, and
doesn't leave it hardcoded.

Signed-off-by: Maxwell Henderson <mxwhenderson@gmail.com>
Change-Id: I1fcc3058538a0bb93d15e1f1591b29b2aa1f62c6
diff --git a/frc971/vision/calibration_accumulator.h b/frc971/vision/calibration_accumulator.h
index 550b691..dbed9ae 100644
--- a/frc971/vision/calibration_accumulator.h
+++ b/frc971/vision/calibration_accumulator.h
@@ -79,7 +79,8 @@
 
 class CalibrationFoxgloveVisualizer {
  public:
-  CalibrationFoxgloveVisualizer(aos::EventLoop *event_loop);
+  CalibrationFoxgloveVisualizer(aos::EventLoop *event_loop,
+                                std::string_view camera_channel = "/camera");
 
   static aos::FlatbufferDetachedBuffer<aos::Configuration>
   AddVisualizationChannels(const aos::Configuration *config,