libstdc++: Remove unused alias template in std::optional

I added this __is_bool alias template in r15-2309-g6d86486292acbe but
it isn't actually used so can be removed.

libstdc++-v3/ChangeLog:

	* include/std/optional (__is_bool): Remove.

diff --git a/libstdc++-v3/include/std/optional b/libstdc++-v3/include/std/optional
index 933a5b15e569eb48c39964b632b879ea8a715054..6a8e76f60e3a636918b6c4427ad0d01259507d2a 100644 (file)
--- a/libstdc++-v3/include/std/optional
+++ b/libstdc++-v3/include/std/optional
@@ -850,8 +850,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        using __not_self = __not_<is_same<optional, __remove_cvref_t<_Up>>>;
       template<typename _Up>
        using __not_tag = __not_<is_same<in_place_t, __remove_cvref_t<_Up>>>;
-      template<typename _Up>
-       using __is_bool = is_same<remove_cv_t<_Up>, bool>;
       template<typename... _Cond>
        using _Requires = enable_if_t<__and_v<_Cond...>, bool>;
 #endif