Merge #13507: RPC: Fix parameter count check for importpubkey

Summary:
3f72d04e29caf247a3fee92f86fe0d250d578914 Fix parameter count check for importpubkey. (Kristaps Kaupe)

Pull request description:

Found this while working on #13464. Parameter count check for `importpubkey` was wrong.

Tree-SHA512: aba41b666c6493379f320be5e3e438a6cad1a96429102ff4428c092c48f29c2eead2195792c0b018296f20e1c42eb091dd5b9886c42cecbb1f0d03d5def14705

Backport of Core PR13507

Test Plan:

ninja
src/bitcoind
src/bitcoin-cli importpubkey "mypubkey" "testing" false 5

Verify RPC error occurs.

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6318