Fix the stencil buffer in Canvases when the graphics driver uses a MSAA value for the Canvas' buffers that's greater than the number of requested MSAA samples.

Fixes https://love2d.org/forums/viewtopic.php?f=4&t=79701

src/modules/graphics/opengl/Canvas.h

@@ -111,7 +111,7 @@ public:
 
 	inline int getMSAA() const
 	{
-		return msaa_samples;
+		return actual_samples;
 	}
 
 	bool resolveMSAA();
@@ -155,7 +155,8 @@ private:
 
 	std::vector<Canvas *> attachedCanvases;
 
-	int msaa_samples;
+	int requested_samples;
+	int actual_samples;
 	bool msaa_dirty;
 
 	size_t texture_memory;