overdraw: Remove redundant v2z/v3z swap

v2z/v3z are unused in the rest of the function since we just rely on v1z
and depth gradients from here on. We already avoided flipping them, so
we also avoid swapping them. This fixes a few clang-tidy warnings.

src/overdrawanalyzer.cpp

@@ -53,11 +53,10 @@ static void rasterize(OverdrawBuffer* buffer, float v1x, float v1y, float v1z, f
 	// flip backfacing triangles to simplify rasterization logic
 	if (sign)
 	{
-		// flipping v2 & v3 preserves depth gradients since they're based on v1
+		// flipping v2 & v3 preserves depth gradients since they're based on v1; only v1z is used below
 		float t;
 		t = v2x, v2x = v3x, v3x = t;
 		t = v2y, v2y = v3y, v3y = t;
-		t = v2z, v2z = v3z, v3z = t;
 
 		// flip depth since we rasterize backfacing triangles to second buffer with reverse Z; only v1z is used below
 		v1z = kViewport - v1z;