Remove duplicate Euclidean length method for Vector

[tianyizheng02]

The Vector class currently has two methods, euclidean_length and magnitude, that both calculate the L2 norm of a vector:

Also I noticed that Vector's euclidLength and magnitude methods both do the same thing. Should I open an issue to have one of them removed?

Let's keep euclidean_length. We can keep the tests of magnitude in euclidean_length

Originally posted by @poyea in #5362 (comment)