build(deps): bump indexmap from 1.5.1 to 1.6.0

Bumps [indexmap](https://github.com/bluss/indexmap) from 1.5.1 to 1.6.0.
- [Release notes](https://github.com/bluss/indexmap/releases)
- [Commits](indexmap-rs/indexmap@1.5.1...1.6.0)

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

Author: dependabot-preview[bot]

Cargo.lock

@@ -31,7 +31,7 @@ jrsonnet-stdlib = { path = "../jrsonnet-stdlib", version = "0.3.0" }
 pathdiff = "0.2.0"
 
 closure = "0.3.0"
-indexmap = "1.5.1"
+indexmap = "1.6.0"
 
 md5 = "0.7.0"
 base64 = "0.12.3"