Update Rust crate indexmap to v2.12.0

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
indexmap	dependencies	minor	=2.11.4 -> =2.12.0

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Release Notes

indexmap-rs/indexmap (indexmap)

v2.12.0

Compare Source

• MSRV: Rust 1.82.0 or later is now required.
• Updated the hashbrown dependency to 0.16 alone.
• Error types now implement core::error::Error.
• Added pop_if methods to IndexMap and IndexSet, similar to the
  method for Vec added in Rust 1.86.

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