minor error in "Multivariable regression - Normalization"

[ohosseini]

In https://github.com/bfortuner/ml-glossary/blob/master/docs/linear_regression.rst at Multivariable regression - Normalization section mentioned:

Our output is a normalized matrix of the same shape with all values between -1 and 1.

while the provided normalize code normalize the input values between -0.5 and 0.5.