[DOCS][NNVM] Delete duplicated tensor operators from list (#1669)

Author: imorinaga

docs/nnvm_top.rst

@@ -136,11 +136,9 @@ This level enables typical convnet models.
    nnvm.symbol.collapse_sum
    nnvm.symbol.broadcast_equal
    nnvm.symbol.broadcast_greater_equal
-   nnvm.symbol.broadcast_greater_equal
    nnvm.symbol.broadcast_greater
    nnvm.symbol.broadcast_left_shift
    nnvm.symbol.broadcast_less_equal
-   nnvm.symbol.broadcast_less_equal
    nnvm.symbol.broadcast_less
    nnvm.symbol.broadcast_max
    nnvm.symbol.broadcast_min
@@ -252,11 +250,9 @@ Detailed Definitions
 .. autofunction:: nnvm.symbol.collapse_sum
 .. autofunction:: nnvm.symbol.broadcast_equal
 .. autofunction:: nnvm.symbol.broadcast_greater_equal
-.. autofunction:: nnvm.symbol.broadcast_greater_equal
 .. autofunction:: nnvm.symbol.broadcast_greater
 .. autofunction:: nnvm.symbol.broadcast_left_shift
 .. autofunction:: nnvm.symbol.broadcast_less_equal
-.. autofunction:: nnvm.symbol.broadcast_less_equal
 .. autofunction:: nnvm.symbol.broadcast_less
 .. autofunction:: nnvm.symbol.broadcast_max
 .. autofunction:: nnvm.symbol.broadcast_min