Update src/nf/nf_layer_constructors.f90

Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Author: milancurcic

src/nf/nf_layer_constructors.f90

@@ -137,7 +137,7 @@ module function conv2d(filters, kernel_width, kernel_height, activation) result(
       !! ```
       !! use nf, only :: conv, layer
       !! type(layer) :: conv2d_layer  
-      !! conv2d_layer = conv2d(filters=32, kernel_width=3, kernel_height=3)
+      !! conv2d_layer = conv(filters=32, kernel_width=3, kernel_height=3)
       !! ```
       integer, intent(in) :: filters
         !! Number of filters in the output of the layer