Merge #10536: Remove unreachable or otherwise redundant code

Summary:
4265bf351 Remove unreachable or otherwise redundant code (practicalswift)

Tree-SHA512: bc9666ab5d20c936d78c50c0361405aca9edd116602aa9bcd71a79a904b647ac9eca0651d1a9d530189a6ac1c4e235bfc69ec1a68f7e36cc14d6848ac2206b7b

Backport of Core PR10536
https://github.com/bitcoin/bitcoin/pull/10536/files

Test Plan:

make check
test_runner.py

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

Reviewed By: jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D3278