Update unindent requirement from 0.1.9 to 0.2.1 (#181)

Updates the requirements on [unindent](https://github.com/dtolnay/indoc) to permit the latest version.
- [Release notes](https://github.com/dtolnay/indoc/releases)
- [Commits](dtolnay/indoc@0.1.9...0.2.1)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

rstest/Cargo.toml

@@ -35,7 +35,7 @@ rstest_reuse = {version = "0.5.0", path = "../rstest_reuse"}
 rstest_test = {version = "0.10.0", path = "../rstest_test"}
 temp_testdir = "0.2.3"
 tokio = {version = "1.19.2", features = ["rt", "macros"]}
-unindent = "0.1.9"
+unindent = "0.2.1"
 
 [build-dependencies]
 rustc_version = "0.4.0"