fix(deps): update rust crate indexmap to v2.8.0

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
indexmap	dependencies	minor	2.7.1 -> 2.8.0

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Release Notes

indexmap-rs/indexmap (indexmap)

v2.8.0

Compare Source

• Added indexmap_with_default! and indexset_with_default! to be used with
  alternative hashers, especially when using the crate without std.
• Implemented PartialEq between each Slice and []/arrays.
• Removed the internal rustc-rayon feature and dependency.

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