[lldb][lldb-dap] Remove unused variable

Fixes warning:
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\lldb\tools\lldb-dap\tool\lldb-dap.cpp(446,27): warning: unused variable 'dap_sessions_condition' [-Wunused-variable]

Variable is unused since #163653 / 5ab3375.

Author: DavidSpickett

lldb/tools/lldb-dap/tool/lldb-dap.cpp

@@ -443,7 +443,6 @@ static llvm::Error serveConnection(
     TrackConnectionTimeout(g_loop, g_connection_timeout_mutex,
                            g_connection_timeout_time_point,
                            connection_timeout_seconds.value());
-  std::condition_variable dap_sessions_condition;
   unsigned int clientCount = 0;
   auto handle = listener->Accept(g_loop, [=, &log, &clientCount](
                                              std::unique_ptr<Socket> sock) {