Bump petgraph from 0.6.0 to 0.6.3

Bumps [petgraph](https://github.com/petgraph/petgraph) from 0.6.0 to 0.6.3.
- [Changelog](https://github.com/petgraph/petgraph/blob/master/RELEASES.rst)
- [Commits](https://github.com/petgraph/petgraph/compare/[email protected]@v0.6.3)

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

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

Author: dependabot[bot]

Cargo.lock

@@ -22,5 +22,5 @@ thiserror = "1"
 regex = "1.0"
 lazy_static = "1.1"
 derive-new = "0.5"
-petgraph = { version = ">=0.5,<0.7", optional = true }
+petgraph = { version = ">=0.5, <0.7", optional = true }
 strum_macros = ">=0.20, <0.25"