chore: make generate_index_ts() deterministic (#451)
chore: make generate_index_ts() deterministic (#451)

Fixes https://github.com/googleapis/synthtool/issues/1103
Source-Link: https://github.com/googleapis/synthtool/commit/c3e41da0fa256ad7f6b4bc76b9d069dedecdfef4
Post-Processor: d10bbe2726487b35bc3a8a9647c94d621cc9801b@sha256:e37a815333a6f3e14d8532efe90cba8aa0d34210f8c0fdbdd9e6a34dcbe51e96
googleapis/google-cloud-node,googleapis/google-cloud-node,googleapis/google-cloud-node,googleapis/google-cloud-node