Update indexmap requirement from 1.7.0 to 2.0.0

Updates the requirements on [indexmap](https://github.com/bluss/indexmap) to permit the latest version.
- [Changelog](https://github.com/bluss/indexmap/blob/master/RELEASES.md)
- [Commits](indexmap-rs/indexmap@1.7.0...2.0.0)

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

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

Author: dependabot[bot]

Cargo.toml

@@ -36,7 +36,7 @@ yaml-rust = { version = "0.4", optional = true }
 rust-ini = { version = "0.18", optional = true }
 ron = { version = "0.8", optional = true }
 json5_rs = { version = "0.4", optional = true, package = "json5" }
-indexmap = { version = "1.7.0", features = ["serde-1"], optional = true}
+indexmap = { version = "2.0.0", features = ["serde-1"], optional = true}
 convert_case = { version = "0.6", optional = true }
 pathdiff = "0.2"