release prep: the sync allowlists build-engine-jars.yml, and test_jvm_payload.py stays out of the upstream pull request #205

The 26.10.1 release rehearsal found two things in the scripts.

The first sync since #141 would prune our own .github/workflows/build-engine-jars.yml, because it was never put on FORK_GITHUB_ALLOWLIST in sync-upstream.sh. The rehearsal had to restore it by hand after the merge.

bindings/python/tests/test_jvm_payload.py crosses into the upstream pull request through make-upstream-pr-branch.sh. It imports benchmarks/experiments/jvm_payload_check.py, which never crosses, so upstream's CI would skip both tests, and its docstring names private filing numbers. It belongs in EXCLUDE_PATHS.

Two crossing workflows cite this repository's issues as bare numbers (issue #10, #12), which read as links to unrelated upstream issues. They get the repository prefix.