Update image_ops_impl.convert_image_dtype.py
Images that are represented using floating point values are expected to have values in the range [0,1) for the function `convert_image_dtype()`.  But this is not scaled when the case `image `argument is of `float ` and `dtype` argument is `int` arises.  Hence modified the code to bring the input values within [0,1). This also shall fix the issue #58749 .