[gcc r15-3616] libstdc++: Remove unused alias template in std::optional

[Jonathan Wakely]

https://gcc.gnu.org/g:f5f55b6e732d119a5c4a1d8e48d1364eb94d9d1d

commit r15-3616-gf5f55b6e732d119a5c4a1d8e48d1364eb94d9d1d
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Sep 12 10:55:23 2024 +0100

    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:
---
 libstdc++-v3/include/std/optional | 2 --
 1 file changed, 2 deletions(-)

diff --git a/libstdc++-v3/include/std/optional b/libstdc++-v3/include/std/optional
index 933a5b15e569..6a8e76f60e3a 100644
--- 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