Update indexmap requirement from 1.6.2 to 2.2.6

Updates the requirements on [indexmap](https://github.com/indexmap-rs/indexmap) to permit the latest version.
- [Changelog](https://github.com/indexmap-rs/indexmap/blob/master/RELEASES.md)
- [Commits](indexmap-rs/indexmap@1.6.2...2.2.6)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

parameterized-macro/Cargo.toml

@@ -23,7 +23,7 @@ path = "tests/cases.rs"
 [dependencies]
 fnv = "1.0.7"
 # from indexmap 2.12 the MSRV is 1.82; unless indexmap needs security updates, a lower MSRV is preferable, since parameterized doesn't need it
-indexmap = { version = "~2.11.4", default-features = false }
+indexmap = { version = "~2.12.0", default-features = false }
 proc-macro2 = "1.0.24"
 quote = "1.0.8"
 syn = { version = "2.0.52", features = ["full"] }