Applications+DevTools+MenuApplets: Drop "unix" pledge when possible

Now that the "unix" pledge is no longer required for socket I/O, we can
drop it after making the connections we need in a program.

In most GUI program cases, once we've connected to the WindowServer by
instantiating a GApplication, we no longer need "unix" :^)

Applications/FileManager/main.cpp

@@ -50,6 +50,11 @@ int main(int argc, char** argv)
 
     GApplication app(argc, argv);
 
+    if (pledge("stdio thread shared_buffer cpath rpath wpath fattr proc exec", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
     auto window = GWindow::construct();
     window->set_title("File Manager");