Fix normal loc scale shape

[michalk8]

• ☑️ I understand it is strictly prohibited to use AI to write PR description
• AI usage disclosure: Fix + test

Fixes the case below - loc/scale/shape cannot broadcast, but silently repeats the values:

import mlx.core as mx
 
mx.random.seed(0)
x = mx.random.normal(shape=(3,), loc=mx.zeros((2, 3)))
# has shape (2, 3), rows are the same
print(x)