[libc++] Fix misplaced _LIBCPP_POP_MACROS

As a drive-by, also remove unnecessary includes from flat container tests.

Closes #134681

Author: ldionne

libcxx/include/istream

@@ -1373,6 +1373,8 @@ extern template class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_iostream<char>;
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #  endif // _LIBCPP_HAS_LOCALIZATION
 
 #  if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
@@ -1382,8 +1384,6 @@ _LIBCPP_END_NAMESPACE_STD
 #    include <type_traits>
 #  endif
 
-_LIBCPP_POP_MACROS
-
 #endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
 
 #endif // _LIBCPP_ISTREAM

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.iterators/reverse_iterator.pass.cpp

@@ -28,7 +28,6 @@
 #include <iterator>
 
 #include "test_macros.h"
-#include <iostream>
 
 int main(int, char**) {
   {

libcxx/test/std/containers/container.adaptors/flat.multimap/flat.multimap.iterators/reverse_iterator.pass.cpp

@@ -30,7 +30,6 @@
 #include <iterator>
 
 #include "test_macros.h"
-#include <iostream>
 
 int main(int, char**) {
   {

libcxx/test/std/containers/container.adaptors/flat.multiset/flat.multiset.iterators/reverse_iterator.pass.cpp

@@ -28,7 +28,6 @@
 #include <iterator>
 
 #include "test_macros.h"
-#include <iostream>
 
 void test() {
   {

libcxx/test/std/containers/container.adaptors/flat.set/flat.set.iterators/reverse_iterator.pass.cpp

@@ -28,7 +28,6 @@
 #include <iterator>
 
 #include "test_macros.h"
-#include <iostream>
 
 void test() {
   {