fuzz: Bump timeout in test_runner to accomodate for slow arm64 CPUs

Summary:
Backport of core PR17470.

Only this commit is relevant:
https://github.com/bitcoin/bitcoin/pull/17470/commits/fa2ec9f4518c1da3ab3592537c6cd204693a6069

Test Plan:

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

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D8139