VideoCommon: drop UpdateViewportWithCorrection

It's only used once in BPFunction which itself is also only used once.
So the setter is moved to BPStructs like all other ones.

Source/Core/VideoCommon/Src/BPStructs.cpp

@@ -185,6 +185,7 @@ void BPWritten(const BPCmd& bp)
 	case BPMEM_SCISSORBR: // Scissor Rectable Bottom, Right
 	case BPMEM_SCISSOROFFSET: // Scissor Offset
 		SetScissor();
+		VertexShaderManager::SetViewportChanged();
 		break;
 	case BPMEM_LINEPTWIDTH: // Line Width
 		SetLineWidth();