`excluded_benchmarks` should list `concurrent_imap` instead of `bench_mp_pool` and `bench_thread_pool`

[colesbury]

bench_runner.toml lists bench_mp_pool and bench_thread_pool in excluded_benchmarks, but the name of the benchmark containing them is concurrent_imap.

https://github.com/faster-cpython/benchmarking-public/blob/e529c1b77a213099817943cb6da12ffc5e56a1d8/bench_runner.toml#L15-L16

https://github.com/python/pyperformance/blob/56d12a8fd7cc1432835965d374929bfa7f6f7a07/pyperformance/data-files/benchmarks/bm_concurrent_imap/pyproject.toml#L9