Cull unused function and its unit test.

Pointed out by: @slackpad

lib/string.go

@@ -13,11 +13,3 @@ func StrContains(l []string, s string) bool {
 	}
 	return false
 }
-
-func ToLowerList(l []string) []string {
-	var out []string
-	for _, value := range l {
-		out = append(out, strings.ToLower(value))
-	}
-	return out
-}

lib/string_test.go

@@ -13,12 +13,3 @@ func TestStrContains(t *testing.T) {
 		t.Fatalf("should not contain")
 	}
 }
-
-func TestToLowerList(t *testing.T) {
-	l := []string{"ABC", "Abc", "abc"}
-	for _, value := range ToLowerList(l) {
-		if value != "abc" {
-			t.Fatalf("failed lowercasing")
-		}
-	}
-}