Refresh polonius wg membership

[lqd]

This refreshes the polonius WG team to actually match its current membership:

• first off, thanks a ton @ecstatic-morse (we miss you),
• @jackh726 has actually been a member for a long time (has reviewed all of my PRs for ever, and has been doing awesome work on the implementation in the last few months. Apologies for the delay in recording this here.

[github-actions]

Dry-run check results

[WARN  rust_team::sync] sync-team is running in dry mode, no changes will be applied.
[INFO  rust_team::sync] synchronizing crates-io
[INFO  rust_team::sync] synchronizing github
[INFO  rust_team::sync] 💻 Team Diffs:
    📝 Editing team 'rust-lang/wg-polonius':
      Adding member 'jackh726' with member role
      Deleting member 'ecstatic-morse'
    💻 Org membership Diffs:
    ❌ Removing the following members from `rust-lang`:
      - ecstatic-morse