[css-color] Typo fix (w3c#1469)

Author: xfq

css-color/Overview.bs

@@ -1795,7 +1795,7 @@ Profiled, Device-dependent Colors</h2>
 	CSS provides two predefined RGB color spaces:
 	image-p3 [[!DCI-P3]],
 	which is a wide gamut space typical of current wide-gamut monitors,
-	and Rec. 2020 [[[!Rec.2020]],
+	and Rec. 2020 [[!Rec.2020]],
 	which is a ultra-wide gamut space capable of representing almost all visible real-world colors.
 	Both are broadcast industry standards.