FIX clip small values in PLS cross-decomposition for increased stabil…

…ity (scikit-learn#13903)

Merge branch 'for0.21.3' into 0.21.X

TST Sets decimal

DOC Improve OPTICS doc (scikit-learn#13866)

DOC Fix reference in whats new 0.21 (scikit-learn#13845)

BLD retagging as 0.21rc2

Version = 0.21rc1

TST use approximate equality for float comparison (scikit-learn#13749)

DOC release dates for 0.20.3

DOC update version to 0.20.2