[backport#15245] remove deprecated mentions of signrawtransaction from fundraw help
[backport#15245] remove deprecated mentions of signrawtransaction from fundraw help

Summary:
851380ce17 remove deprecated mentions of signrawtransaction from fundraw help (Gregory Sanders)

Pull request description:

  RPC call has been removed as of 0.17.99.

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Backport of Core [[https://github.com/bitcoin/bitcoin/pull/15245 | PR15245]]

Test Plan:
  none

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6846

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