build(deps): bump org.spockframework:spock-core

Bumps [org.spockframework:spock-core](https://github.com/spockframework/spock) from 2.4-M5-groovy-4.0 to 2.4-M6-groovy-4.0.
- [Release notes](https://github.com/spockframework/spock/releases)
- [Changelog](https://github.com/spockframework/spock/blob/master/docs/release_notes.adoc)
- [Commits](https://github.com/spockframework/spock/commits)

---
updated-dependencies:
- dependency-name: org.spockframework:spock-core
  dependency-version: 2.4-M6-groovy-4.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

build.gradle.kts

@@ -20,7 +20,7 @@ dependencies {
   testImplementation("org.junit.jupiter:junit-jupiter-api:5.11.4")
   testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine:5.11.4")
 
-  testImplementation("org.spockframework:spock-core:2.4-M5-groovy-4.0")
+  testImplementation("org.spockframework:spock-core:2.4-M6-groovy-4.0")
 
   javacc("net.java.dev.javacc:javacc:7.0.13")
 }