[Scorecards] Darken success colour

This way it can pass contrast test against green-100

scoring/static/scoring/scss/variables.scss

@@ -5,7 +5,7 @@ $color-scorecard-pink: #9e0d7a;
 $color-scorecard-red: #7c0006;
 $color-scorecard-orange: #f29e1a;
 $color-scorecard-yellow: #ffd80b;
-$color-scorecard-green: #038966;
+$color-scorecard-green: #02694d;
 $color-scorecard-cyan: #1b97a0;
 $color-scorecard-grey-100: #f3f6fb;
 $color-scorecard-grey-200: #ecf0f5;