Bump liquid from 0.20.1 to 0.21.1

Bumps [liquid](https://github.com/cobalt-org/liquid-rust) from 0.20.1 to 0.21.1.
- [Release notes](https://github.com/cobalt-org/liquid-rust/releases)
- [Changelog](https://github.com/cobalt-org/liquid-rust/blob/master/CHANGELOG.md)
- [Commits](https://github.com/cobalt-org/liquid-rust/compare/liquid-bin-v0.20.1...liquid-lib-v0.21.1)

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

Cargo.toml

@@ -80,7 +80,7 @@ predicates = "1.0.5"
 
 [build-dependencies]
 clap = { version = "2.33", optional = true }
-liquid = { version = "0.20", optional = true }
+liquid = { version = "0.21", optional = true }
 
 [profile.release]
 lto = true