Bump subxt from 1c5faf3 to a7b45ef

Bumps [subxt](https://github.com/paritytech/subxt) from `1c5faf3` to `a7b45ef`.
- [Release notes](https://github.com/paritytech/subxt/releases)
- [Commits](paritytech/subxt@1c5faf3...a7b45ef)

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

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

Author: dependabot[bot]