Bump avail-subxt from v1.6.3 to v1.8.0.5

Bumps [avail-subxt](https://github.com/availproject/avail) from v1.6.3 to v1.8.0.5.
- [Release notes](https://github.com/availproject/avail/releases)
- [Commits](availproject/avail@b4feb4a...ebfdac9)

---
updated-dependencies:
- dependency-name: avail-subxt
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>