removing repeated average function implementation and docs rendering

[fnhirwa]

Closes #13853

The function jax.numpy.average is repeated many times on the documentation page jax.numpy.average

This PR removes duplicated code that caused the issue
Thanks

[jakevdp]

Thanks - I don't think this is the right fix. These typing overloads do serve a purpose: they ensure that when the function is used in typechecked code, the static type checker can infer the correct number of outputs. If your goal is fixing the docs, I'd suggest modifying the docs rather than the source code.

This documentation is generated via sphinx autodoc: perhaps that extension has settings that control how overloaded function definitions are displayed?

[fnhirwa]

Yeah sure it is the issue with sphinx
you're right there might be support for this as if it is many overloads it may seem very weird

[jakevdp]

#13860 improves the situation somewhat by preserving the ArrayLike alias rather than printing out the full union it represents.

[fnhirwa]

I think as these function overloading are needed we can close this PR