sort: clarify doc on less

src/sort/sort.go

@@ -21,15 +21,14 @@ type Interface interface {
 	// Less reports whether the element with index i
 	// must sort before the element with index j.
 	//
+	// Less must satisfy strict weak ordering.
+	// https://en.wikipedia.org/wiki/Weak_ordering#Strict_weak_orderings
+	//
 	// If both Less(i, j) and Less(j, i) are false,
 	// then the elements at index i and j are considered equal.
 	// Sort may place equal elements in any order in the final result,
 	// while Stable preserves the original input order of equal elements.
 	//
-	// Less must describe a transitive ordering:
-	//  - if both Less(i, j) and Less(j, k) are true, then Less(i, k) must be true as well.
-	//  - if both Less(i, j) and Less(j, k) are false, then Less(i, k) must be false as well.
-	//
 	// Note that floating-point comparison (the < operator on float32 or float64 values)
 	// is not a transitive ordering when not-a-number (NaN) values are involved.
 	// See Float64Slice.Less for a correct implementation for floating-point values.