[lldb] Fix a warning

This patch fixes:

  lldb/source/Core/Debugger.cpp:1002:10: error: lambda capture 'this'
  is not used [-Werror,-Wunused-lambda-capture]

Author: kazutakahirata

lldb/source/Core/Debugger.cpp

@@ -1001,6 +1001,7 @@ void Debugger::Clear() {
     telemetry::ScopedDispatcher<telemetry::DebuggerInfo> helper(
         [this](lldb_private::telemetry::DebuggerInfo *info) {
           assert(this == info->debugger);
+          (void)this;
           info->is_exit_entry = true;
         },
         this);