Reduce contrast between scope and item background colors

Still seems enough, and decreases probability of ending up with difficult
to read text and background color combination.

modules/templates/helper.go

@@ -834,7 +834,7 @@ func RenderLabel(label *issues_model.Label) string {
 		// Make scope and item background colors slightly darker and lighter respectively.
 		// More contrast needed with higher luminance, empirically tweaked.
 		luminance := (0.299*r + 0.587*g + 0.114*b) / 255
-		contrast := 0.01 + luminance*0.06
+		contrast := 0.01 + luminance*0.03
 		// Ensure we add the same amount of contrast also near 0 and 1.
 		darken := contrast + math.Max(luminance+contrast-1.0, 0.0)
 		lighten := contrast + math.Max(contrast-luminance, 0.0)