test(run-store): drop mock-based waitpoint fan-out test; main's nShardMatrix covers it

Main's runOpsStore.nShardMatrix.test.ts is a four-store testcontainer matrix
that already guards the N-way waitpoint fan-out on real databases — the
gen-2-shard union with no double count, the mirrored-cuid case, alias dedup,
and cross-tree completion. The removed test used fakeStore() stubs, which both
duplicates that coverage and violates the repo's "never mock, use
testcontainers" rule (CodeRabbit). Removing it also clears the code-quality
oxfmt --check failure the unformatted file caused.

Author: d-cs