[RFC] Minimal scipy version for 1.0 (or 0.26) release

I'd like to propose to increase the minimal scipy version to 1.0.

SCIPY_MIN_VERSION = '1.0.0'

In case we should release scikit-learn 1.0, it would be a good fit:smirk:
Linear quantile regression [MRG] Add quantile regression #9978 could make it into the next release. It uses scipy.optimize.linprog under the hood. Scipy 1.0.0 has introduced a new solver method="interior-point" which is set as default method. Having it available would help us to avoid to support the "simplex" method in scikit-learn. Note, that scipy v1.3.0 introduced the "revised simplex" method and version 1.5 the "highs**" solvers which are much preferred.
I think we should avoid the legacy simplex method.
Your reason for scipy 1.0.0.

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