libstdc++: Use new <bits/monostate.h> header in <format>

In r15-5832-g91f4550e1700b7 std::monostate was moved to its own header,
which means that <format> no longer needs to include all of <variant>.

libstdc++-v3/ChangeLog:

	* include/std/format: Include <bits/monostate.h> instead of
	<variant>.

diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index bc26599b9f97b1a7d1f2cd792c142595ada9da8a..f52645a3ac756f9b1c62fce8463dcf0820d3d58f 100644 (file)
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -51,7 +51,7 @@
 #include <span>
 #include <string_view>
 #include <string>
-#include <variant>            // monostate (TODO: move to bits/utility.h?)
+#include <bits/monostate.h>
 #include <bits/ranges_base.h>  // input_range, range_reference_t
 #include <bits/ranges_util.h>  // subrange
 #include <bits/ranges_algobase.h> // ranges::copy