Describe the measured tone and vibrance in DarkRoom's own terms

The calibration commits named DarkRoom's default curve after another
product and described vibrance as doing what another editor's does at
the same value. The curve is the DNG SDK's reference, so it is called
that; vibrance is scaled to deliver the strength its value names, as
measured against the photographer's earlier exports. Two test names
follow. The measurements and where they came from are unchanged.

core/dr-pipeline/src/camera_raw.rs

@@ -113,7 +113,7 @@ mod tests {
     }
 
     #[test]
-    fn the_default_adds_the_contrast_lightroom_showed() {
+    fn the_default_adds_the_measured_contrast() {
         // Fitted on Lightroom exports with neutral settings (D21 addendum):
         // the bare reference curve is a little flat against them.
         let p = contrast_power(DEFAULT_CONTRAST);