Simplify dwrite.dll loading process (#6538)

* Simplify dwrite loading process

All supported OS always has `dwrite.dll`.

* Remove noop

src/Microsoft.DotNet.Wpf/src/Shared/cpp/dwriteloader.cpp

@@ -7,37 +7,9 @@
 namespace WPFUtils
 {
 
-#if defined(__cplusplus_cli)
-#endif
 HMODULE LoadDWriteLibraryAndGetProcAddress(void **pfncptrDWriteCreateFactory)
 {
-    HMODULE hDWriteLibrary = nullptr;
-    
-    // KB2533623 introduced the LOAD_LIBRARY_SEARCH_SYSTEM32 flag. It also introduced
-    // the AddDllDirectory function. We test for presence of AddDllDirectory as an 
-    // indirect evidence for the support of LOAD_LIBRARY_SEARCH_SYSTEM32 flag. 
-    HMODULE hKernel32 = GetModuleHandle(L"kernel32.dll");
-    if (hKernel32 != nullptr)
-    {
-        if (GetProcAddress(hKernel32, "AddDllDirectory") != nullptr)
-        {
-            // All supported platforms newer than Vista SP2 shipped with dwrite.dll.
-            // On Vista SP2, the .NET servicing process will ensure that a MSU containing 
-            // dwrite.dll will be delivered as a prerequisite - effectively guaranteeing that 
-            // this following call to LoadLibraryEx(dwrite.dll) will succeed, and that it will 
-            // not be susceptible to typical DLL planting vulnerability vectors.
-            hDWriteLibrary = LoadLibraryEx(L"dwrite.dll", nullptr, LOAD_LIBRARY_SEARCH_SYSTEM32);
-        }
-        else 
-        {
-            // LOAD_LIBRARY_SEARCH_SYSTEM32 is not supported on this OS. 
-            // Fall back to using plain ol' LoadLibrary
-            // There is risk that this call might fail, or that it might be
-            // susceptible to DLL hijacking. 
-            hDWriteLibrary = LoadLibrary(L"dwrite.dll");
-        }
-    }
-    
+    HMODULE hDWriteLibrary = LoadLibraryEx(L"dwrite.dll", nullptr, LOAD_LIBRARY_SEARCH_SYSTEM32);
     if (hDWriteLibrary)
     {
         *pfncptrDWriteCreateFactory = GetProcAddress(hDWriteLibrary, "DWriteCreateFactory");