Base: Remove the cpp-gui HackStudio template

This template is essentially an older version of the
serenity-application template, it does not compile anymore and is
therefore entirely redundant.

Base/res/devel/templates/cpp-gui.ini

@@ -1,5 +0,0 @@
-[HackStudioTemplate]
-Name=Graphical Application (C++)
-Description=Template for creating a basic C++ graphical application.
-Priority=90
-IconName32x=cpp-gui

Base/res/devel/templates/cpp-gui.postcreate

@@ -1,22 +0,0 @@
-#!/bin/Shell
-
-echo > $2/Makefile <<-EOF
-PROGRAM = $1
-OBJS = main.o
-CXXFLAGS = -g -std=c++2a
-LDFLAGS = -lgui -lgcc_s
-
-all: \$(PROGRAM)
-
-\$(PROGRAM): \$(OBJS)
-	\$(CXX) \$(LDFLAGS) -o \$@ \$(OBJS)
-
-%.o: %.cpp
-	\$(CXX) \$(CXXFLAGS) -o \$@ -c \$<
-
-clean:
-	rm \$(OBJS) \$(PROGRAM)
-
-run:
-	./\$(PROGRAM)
-EOF

Base/res/devel/templates/cpp-gui/main.cpp

@@ -1,26 +0,0 @@
-#include <LibGUI/Application.h>
-#include <LibGUI/Button.h>
-#include <LibGUI/MessageBox.h>
-#include <LibGUI/Window.h>
-#include <stdio.h>
-
-int main(int argc, char** argv)
-{
-    auto app = GUI::Application::construct(argc, argv);
-
-    auto window = GUI::Window::construct();
-    window->set_title("Hello friends!");
-    window->resize(200, 100);
-
-    auto button = GUI::Button::construct();
-    button->set_text("Click me!");
-    button->on_click = [&](auto) {
-        GUI::MessageBox::show(window, "Hello friends!"sv, ":^)"sv);
-    };
-
-    window->set_main_widget(button);
-
-    window->show();
-
-    return app->exec();
-}