Bump toml from 0.7.4 to 0.7.5 (#533)

* Bump toml from 0.7.4 to 0.7.5

Bumps [toml](https://github.com/toml-rs/toml) from 0.7.4 to 0.7.5.
- [Commits](toml-rs/toml@toml-v0.7.4...toml-v0.7.5)

---
updated-dependencies:
- dependency-name: toml
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

* Use major versions only in Cargo.toml

For consistency with our other lockfile-using repos, and to avoid
Dependabot PR conflicts.

* Refresh Cargo.lock

---------

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Ed Morley <[email protected]>