Always show the same help topic regardless of wallet flags, and explain that something is not always available, rather than runtime-modifying the help output.
https://github.com/bitcoin/bitcoin/pull/16239/commits/53c3c1ea9e20f881c843a9219e48cec202e962f8
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Partial backport of Core [[https://github.com/bitcoin/bitcoin/pull/16239 | PR16239]]