chore: update @PolkaDot and eslint dependencies to latest versions (#2270)

# Goal
The goal of this PR is to update polkadot.js to the latest api, 15.8.2

# Checklist
- [ ] Updated Pallet Readme?
- [x] Updated js/api-augment for Custom RPC APIs?
- [ ] Design doc(s) updated?
- [ ] Unit Tests added?
- [ ] e2e Tests added?
- [ ] Benchmarks added?
- [ ] Spec version incremented?

Author: mattheworris