[libc++] Remove <ostream> include from <chrono> (#96035)

diff --git a/libcxx/include/__chrono/ostream.h b/libcxx/include/__chrono/ostream.h
index ecf07a3..bb0341b 100644
--- a/libcxx/include/__chrono/ostream.h
+++ b/libcxx/include/__chrono/ostream.h
@@ -30,7 +30,7 @@
 #include <__concepts/same_as.h>
 #include <__config>
 #include <__format/format_functions.h>
-#include <ostream>
+#include <__fwd/ostream.h>
 #include <ratio>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/chrono b/libcxx/include/chrono
index c1a92595..c66771f 100644
--- a/libcxx/include/chrono
+++ b/libcxx/include/chrono
@@ -997,6 +997,7 @@
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER == 20
 #  include <charconv>
 #  include <locale>
+#  include <ostream>
 #endif
 
 #endif // _LIBCPP_CHRONO
diff --git a/libcxx/test/libcxx/transitive_includes/cxx23.csv b/libcxx/test/libcxx/transitive_includes/cxx23.csv
index bfb8b5d..4cad0fd 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx23.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx23.csv
@@ -75,7 +75,6 @@
 chrono format
 chrono forward_list
 chrono limits
-chrono ostream
 chrono ratio
 chrono sstream
 chrono stdexcept
diff --git a/libcxx/test/libcxx/transitive_includes/cxx26.csv b/libcxx/test/libcxx/transitive_includes/cxx26.csv
index bfb8b5d..4cad0fd 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx26.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx26.csv
@@ -75,7 +75,6 @@
 chrono format
 chrono forward_list
 chrono limits
-chrono ostream
 chrono ratio
 chrono sstream
 chrono stdexcept