Update Rust crate indexmap to 1.9.3

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
indexmap	dependencies	patch	1.9 -> 1.9.3

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Release Notes

indexmap-rs/indexmap (indexmap)

v1.9.3

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• Bump the rustc-rayon dependency, for compiler use only.

v1.9.2

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• IndexMap and IndexSet both implement arbitrary::Arbitrary<'_> and
  quickcheck::Arbitrary if those optional dependency features are enabled.

v1.9.1

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• The MSRV now allows Rust 1.56.0 as well. However, currently hashbrown
  0.12.1 requires 1.56.1, so users on 1.56.0 should downgrade that to 0.12.0
  until there is a later published version relaxing its requirement.

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