Merge #12503: [RPC] createmultisig no longer takes addresses

Summary:
e4c924c517 createmultisig no longer takes addresses (Gregory Sanders)

Pull request description:
Removed mention of address in help text.

Tree-SHA512: a6a752ef2282c5c893dd1a6ff5ccab42d3de1989847af627d82d41605ea19abc0aaf68567a62b6478933ba7eea09f911087b410ba7d3a815331ef15ec1ff9df0

Backport of Core PR12503
https://github.com/bitcoin/bitcoin/pull/12503/

Test Plan:

make check
./bitcoind
./bitcoin-cli help createmultisig

Reviewers: deadalnix, Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D4022