Override default `clearBit` method impl for `Natural`
Override default `clearBit` method impl for `Natural`

The default implementation of `clearBit` is in terms of
`complement`. However, `complement` is not well-defined
for `Natural` and this consequently renders the default
implementation of `clearBit` dysfunctional.

This implements `clearBit` in terms of `testBit`
and `setBit` which are both well-defined for `Natural`s.

This addresses #13203

sdiehl/ghc,ezyang/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,ezyang/ghc,sdiehl/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc