[backport#17138 2/2][wallet] Remove pruning check for -rescan option

Summary:
Prior to this PR, the wallet would not allow the -rescan option at
startup if pruning was enabled. This is unnecessarily restrictive. It
should be possible to rescan if pruning is enabled, as long as no blocks
have actually been pruned yet.

Remove the pruning check from WalletInit::ParameterInteraction(). If any
blocks have been pruned, that will be caught in CreateWalletFromFile().

https://github.com/bitcoin/bitcoin/pull/17138/commits/b96ed0396294fc4fa89d83ceab6bc169dd09f002

Depends on D7090

Concludes backport of Core PR17138

Test Plan:

ninja check check-functional

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7091