This harmonizes the wording of operator= semantics for all four type-erasure types (function, any, move_only_function, copyable_function) by bringing the former two into line with the latter (newer) two.

Using "Equivalent to" instead of "As if by" allows us to omit some wording about what exceptions might be thrown. [func.wrap.func.con] also had a typo "As if by x;" that should have been "As if by x."

The one borderline-editorial part is function's move-constructor ([func.wrap.func.cons]/21). The old wording is
"Replaces the target of *this with the target of f," which a sufficiently smart vendor could take as giving permission to use the contained object's assignment operator (if f's contained object is assignable to *this's contained object) and/or to destroy *this's contained object before copying f's contained object. My impression is that no vendor (ab)uses that permission today, but please correct me if I'm wrong.