Reset fuzzer missing corpora

Summary:
The https://github.com/Bitcoin-ABC/qa-assets repo has been updated so
there is no missing corpus anymore.

Test Plan:

ninja bitcoin-fuzzers
./test/fuzz/test_runner.py <path_to_corpus>

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D8144