Remove the lock entirely as per PR discussion

Correctly unlock mutex before its destruction

As per https://en.cppreference.com/w/cpp/thread/mutex/~mutex destroying a locked mutex is undefined behavior and MSVC++ decides to throw in this case

Swap out unique for scoped lock and readd comment

src/core/hle/kernel/service_thread.cpp

@@ -163,9 +163,6 @@ ServiceThread::Impl::~Impl() {
     m_wakeup_event->Signal();
     m_host_thread.join();
 
-    // Lock mutex.
-    m_session_mutex.lock();
-
     // Close all remaining sessions.
     for (const auto& [server_session, manager] : m_sessions) {
         server_session->Close();