Support newest `pgvector` versions

[Our current extension version constraint](https://github.com/geldata/gel/blob/09ce1ee8097744d19e73c65ff43d264135e71f98/edb/lib/ext/pgvector.edgeql#L22) does not include the latest two versions that have come out in the last year. Some online Postgres vendors (notably Google's Cloud SQL for Postgres) only include `0.8.0` which was released in October 2024.