Update Rust crate indexmap to v2.6.0

Author: renovate[bot]

Cargo.lock

@@ -83,7 +83,7 @@ hex = "=0.4.3"
 http = "=1.1.0"
 http-body-util = "=0.1.2"
 hyper = { version = "=1.4.1", features = ["client", "http1"] }
-indexmap = { version = "=2.5.0", features = ["serde"] }
+indexmap = { version = "=2.6.0", features = ["serde"] }
 indicatif = "=0.17.8"
 ipnetwork = "=0.20.0"
 tikv-jemallocator = { version = "=0.6.0", features = ['unprefixed_malloc_on_supported_platforms', 'profiling'] }