Bumps [subxt](https://github.com/paritytech/subxt) from `1c5faf3` to `a7b45ef`.
- [Release notes](https://github.com/paritytech/subxt/releases)
- [Commits](https://github.com/paritytech/subxt/compare/1c5faf3f8f79cbba5bd51fe3042d47584beb54ef...a7b45ef1d13f257d66ecb3775c0b100954618c71)

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

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