Do not implement Module for BatchNorm. (#1513)

candle-examples/examples/yolo-v3/darknet.rs

@@ -147,7 +147,7 @@ fn conv(vb: VarBuilder, index: usize, p: usize, b: &Block) -> Result<(usize, Bl)
     let func = candle_nn::func(move |xs| {
         let xs = conv.forward(xs)?;
         let xs = match &bn {
-            Some(bn) => bn.forward(&xs)?,
+            Some(bn) => xs.apply_t(bn, false)?,
             None => xs,
         };
         let xs = if leaky {