Set lower-bound pins for Pgvector

[anakin87]

More details in the parent issue.

For each integration with errors, we should follow these steps:

• set correct lower-bound pins for direct dependencies in pyproject.toml (this should ensure that the script runs without errors)
• add a CI job in the relevant workflow to check this aspect (example in ci: check lowest direct dependencies #1788)
• when the PR is merged, release a new version of the integration
  • if we are sure to have found the minimum lower bound, a new bugfix version can be released (X.Y.Z+1)
  • if for some reason we were not able to find the minimum lower bound, this is technically a breaking change, so we should release a new major version (X+1.Y.Z)