test: enable txindex in feature_init
Summary:
Now that core#23365 is merged.
core#23365 was backported in D11299
This concludes backport of core#23737
https://github.com/bitcoin/bitcoin/pull/23737/commits/8904f17ea715f3d28f18c1b8ce46a39ff2076144
Depends on D12614
Test Plan: ninja check-functional
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D12615