Bump org.testcontainers:spock from 1.17.6 to 1.21.1 (#925)

Bumps [org.testcontainers:spock](https://github.com/testcontainers/testcontainers-java) from 1.17.6 to 1.21.1.
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.17.6...1.21.1)

---
updated-dependencies:
- dependency-name: org.testcontainers:spock
  dependency-version: 1.21.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

build.gradle.kts

@@ -73,7 +73,7 @@ dependencies {
         exclude("org.eclipse.jgit", "org.eclipse.jgit.ui")
         exclude("org.eclipse.jgit", "org.eclipse.jgit")
     }
-    testImplementation("org.testcontainers:spock:1.17.6")
+    testImplementation("org.testcontainers:spock:1.21.1")
     testImplementation("org.spockframework:spock-core:2.3-groovy-3.0")
     testImplementation("org.spockframework:spock-junit4:2.3-groovy-3.0")
     testImplementation("cglib:cglib-nodep:3.3.0")