Fixes warning after #8877.
Removed warning:
qt/rpcconsole.cpp:173:56: warning: declaration shadows a local variable [-Wshadow]
auto add_to_current_stack = [&](const std::string& curarg) {
^
qt/rpcconsole.cpp:167:17: note: previous declaration is here
std::string curarg;
^
1 warning generated.