Fix errors from new cpplint.py (#7105)

wpigui/src/main/native/cpp/wpigui.cpp

@@ -10,7 +10,9 @@
 #include <chrono>
 #include <cstdio>
 #include <cstring>
+#include <string>
 #include <thread>
+#include <utility>
 
 #include <GLFW/glfw3.h>
 #include <IconsFontAwesome6.h>

wpigui/src/main/native/cpp/wpigui_openurl.cpp

@@ -14,6 +14,8 @@
 #include <unistd.h>
 #endif
 
+#include <string>
+
 void wpi::gui::OpenURL(const std::string& url) {
 #ifdef _WIN32
   ShellExecuteA(nullptr, "open", url.c_str(), nullptr, nullptr, SW_SHOWNORMAL);