Fix Windows build errors introduced in D2765

Summary:
See core issue #12386:
bitcoin/bitcoin#12386

Backport of core PR12416

Test Plan:
  make check
Build the windows binaries

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: schancel

Differential Revision: https://reviews.bitcoinabc.org/D2779

src/qt/bitcoin.cpp

@@ -793,7 +793,7 @@ int main(int argc, char *argv[]) {
         WinShutdownMonitor::registerShutdownBlockReason(
             QObject::tr("%1 didn't yet exit safely...")
                 .arg(QObject::tr(PACKAGE_NAME)),
-            static_cast<HWND>(app.getMainWinId()));
+            (HWND)app.getMainWinId());
 #endif
         app.exec();
         app.requestShutdown(config);

src/qt/winshutdownmonitor.cpp

@@ -56,9 +56,8 @@ bool WinShutdownMonitor::nativeEventFilter(const QByteArray &eventType,
 void WinShutdownMonitor::registerShutdownBlockReason(const QString &strReason,
                                                      const HWND &mainWinId) {
     typedef BOOL(WINAPI * PSHUTDOWNBRCREATE)(HWND, LPCWSTR);
-    PSHUTDOWNBRCREATE shutdownBRCreate =
-        static_cast<PSHUTDOWNBRCREATE>(GetProcAddress(
-            GetModuleHandleA("User32.dll"), "ShutdownBlockReasonCreate"));
+    PSHUTDOWNBRCREATE shutdownBRCreate = (PSHUTDOWNBRCREATE)GetProcAddress(
+        GetModuleHandleA("User32.dll"), "ShutdownBlockReasonCreate");
     if (shutdownBRCreate == nullptr) {
         qWarning() << "registerShutdownBlockReason: GetProcAddress for "
                       "ShutdownBlockReasonCreate failed";