Update petgraph requirement from 0.6.2 to 0.7.1

Updates the requirements on [petgraph](https://github.com/petgraph/petgraph) to permit the latest version.
- [Changelog](https://github.com/petgraph/petgraph/blob/master/RELEASES.rst)
- [Commits](https://github.com/petgraph/petgraph/compare/[email protected]@v0.7.1)

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

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

datafusion/physical-expr/Cargo.toml

@@ -52,7 +52,7 @@ indexmap = { workspace = true }
 itertools = { workspace = true, features = ["use_std"] }
 log = { workspace = true }
 paste = "^1.0"
-petgraph = "0.6.2"
+petgraph = "0.7.1"
 
 [dev-dependencies]
 arrow = { workspace = true, features = ["test_utils"] }