Update pubs.opengroup.org links for POSIX 2024 (and https).

Change-Id: I5ac55398561c3da5b7915a479dbbb709ae98c758
diff --git a/tests/wchar_test.cpp b/tests/wchar_test.cpp
index 387d23b..a811fd8 100644
--- a/tests/wchar_test.cpp
+++ b/tests/wchar_test.cpp
@@ -556,7 +556,7 @@
   } else {
     // If the subject sequence begins with a <hyphen-minus>, the value resulting
     // from the conversion shall be negated.
-    // http://pubs.opengroup.org/onlinepubs/9699919799/functions/strtoul.html
+    // https://pubs.opengroup.org/onlinepubs/9799919799.2024edition/functions/strtoul.html
     ASSERT_EQ(std::numeric_limits<T>::max(), fn(min_str, nullptr, 0)) << min_str;
   }
   ASSERT_EQ(std::numeric_limits<T>::max(), fn(max_str, nullptr, 0)) << max_str;