Update indexmap dependency to version 2

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [nightly, beta, stable, 1.58.0]
+        rust: [nightly, beta, stable, 1.64.0]
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v3

Cargo.toml

@@ -9,10 +9,10 @@ edition = "2021"
 keywords = ["yaml", "serde", "serialization"]
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/dtolnay/serde-yaml"
-rust-version = "1.58"
+rust-version = "1.64"
 
 [dependencies]
-indexmap = { version = "1.9", features = ["std"] }
+indexmap = "2"
 itoa = "1.0"
 ryu = "1.0"
 serde = "1.0.139"