Update `dnn_conv3d()` entry into conv doc.

doc/library/tensor/nnet/conv.txt

@@ -107,14 +107,12 @@ not need to read it. Theano will select it for you.
       replacement for nnet.conv3d. For convolutions done on CPU,
       nnet.conv3d will be replaced by Corr3dMM.
 
-    - :func:`dnn_conv <theano.gpuarray.dnn.dnn_conv>` GPU-only
-      convolution using NVIDIA's cuDNN library.
+    - :func:`dnn_conv3d <theano.gpuarray.dnn.dnn_conv3d>` GPU-only
+      3D convolution using NVIDIA's cuDNN library (as :func:`dnn_conv <theano.gpuarray.dnn.dnn_conv>` but for 3d).
 
       If cuDNN is available, by default, Theano will replace all nnet.conv3d
       operations with dnn_conv.
 
-    - :func:`dnn_conv3d <theano.gpuarray.dnn.dnn_conv3d>` as dnn_conv() but for 3d.
-
     - :func:`conv3d2d <theano.tensor.nnet.conv3d2d.conv3d>`
       Another conv3d implementation that uses the conv2d with data reshaping.
       It is faster in some corner cases than conv3d. It flips the kernel.