Fix peak_local_max's output for ndarray when indices is set to False

Dear skimage team, the `peak_local_max` func in `feature` module accept a ndarray and return its peak bool image when input parameter `indices=False`. 

However, this functionality seemed just taking 2d image into consideration, when input array is higher than 2d, the output is akward.

This PR extends this functionality into ndarrays.