Assert: Uppercase assertion macros

Macros should be all upper-cased. This is also kind of a wart that's
been sticking out for quite a while now (we avoid prefixing
underscores).

Source/Core/VideoBackends/Vulkan/VKShader.cpp

@@ -34,7 +34,7 @@ VKShader::~VKShader()
 
 bool VKShader::HasBinary() const
 {
-  _assert_(!m_spv.empty());
+  ASSERT(!m_spv.empty());
   return true;
 }