media-video/mkvtoolnix: remove unused patch

Signed-off-by: Petr Vaněk <arkamar@gentoo.org>

media-video/mkvtoolnix/files/mkvtoolnix-84.0.0-fix-libcxx-c++20.patch

@@ -1,44 +0,0 @@
-https://bugs.gentoo.org/933417
-https://gitlab.com/mbunkus/mkvtoolnix/-/issues/3695
-https://gitlab.com/mbunkus/mkvtoolnix/-/commit/7e1bea9527616ab6ab38425e7290579f05dd9bb1
-
-From 7e1bea9527616ab6ab38425e7290579f05dd9bb1 Mon Sep 17 00:00:00 2001
-From: Moritz Bunkus <mo@bunkus.online>
-Date: Tue, 30 Apr 2024 16:05:35 +0200
-Subject: [PATCH] replace removed `std::result_of` with `std::invoke_result`
-
-`std::result_of` was deprecated in C++17 & removed in C++20. A lot of
-compilers still make it available even when running in C++20 mode,
-while others don't.
-
-Therefore replace it with equivalent use of `std::invoke_result`.
-
-Fixes #3695.
---- a/NEWS.md
-+++ b/NEWS.md
-@@ -1,3 +1,11 @@
-+# Version ?
-+
-+## Bug fixes
-+
-+* fixed compilation of `src/common/sorting.h` with certain compilers due to
-+  the deprecation & removal of `std::result_of<>` in C++20. Fixes #3695.
-+
-+
- # Version 84.0 "Sleeper" 2024-04-28
- 
- ## New features and enhancements
---- a/src/common/sorting.h
-+++ b/src/common/sorting.h
-@@ -27,7 +27,7 @@ namespace mtx::sort {
- 
- template<  typename Titer
-          , typename Tcriterion_maker
--         , typename Tcriterion = typename std::result_of< Tcriterion_maker(typename std::iterator_traits<Titer>::value_type) >::type
-+         , typename Tcriterion = typename std::invoke_result< Tcriterion_maker, typename std::iterator_traits<Titer>::value_type >::type
-          , typename Tcomparator = std::less<Tcriterion>
-          >
- void
--- 
-GitLab
-