fixes noise added to spectral embedding

[tomhaber]

The same (scalar) noise is added to all values in the spectral embedding. Noise should actually be added to every point/coordinate independently.

[dillondaudert]

Broadcasting the randn should generate independent noise for each element. Perhaps you could clarify what the change here does with an example?

[tomhaber]

Oh wow, I did not expect that behavior at all. My change does exactly the same then