This RPC lists all the descriptors present in the wallet, not only
the ones that were imported, but also the ones generated when a
new wallet is created.
It can be verified by creating a new wallet and calling the
`listdescriptors` RPC, which will contain 8 ranged descriptors that
are created for every new wallet.
Also, update the description to get rid of "descriptor-enabled"
because this is the only wallet type available now after removal of
legacy wallets.
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