Fix dialyzer, no error on cache_put

[vihu]

Problem

Dialyzer complains on master branch with:

src/ledger/v1/blockchain_ledger_v1.erl
Line 2194 Column 37: The variable _ can never match since previous clauses completely covered the type 'ok'

Solution

blockchain_ledger_v1:cache_put can never actually return any error, this propagates that up the stack and fixes the call to promote_to_public_poc/2.