Bump creekVersion from 0.3.1-SNAPSHOT to 0.3.1 (#137)

Bumps `creekVersion` from 0.3.1-SNAPSHOT to 0.3.1.

Updates `creek-test-util` from 0.3.1-SNAPSHOT to 0.3.1
- [Release notes](https://github.com/creek-service/creek-test/releases)
- [Commits](https://github.com/creek-service/creek-test/commits/v0.3.1)

Updates `creek-test-hamcrest` from 0.3.1-SNAPSHOT to 0.3.1
- [Release notes](https://github.com/creek-service/creek-test/releases)
- [Commits](https://github.com/creek-service/creek-test/commits/v0.3.1)

Updates `creek-test-conformity` from 0.3.1-SNAPSHOT to 0.3.1
- [Release notes](https://github.com/creek-service/creek-test/releases)
- [Commits](https://github.com/creek-service/creek-test/commits/v0.3.1)

---
updated-dependencies:
- dependency-name: org.creekservice:creek-test-util
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.creekservice:creek-test-hamcrest
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.creekservice:creek-test-conformity
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

build.gradle.kts

@@ -25,7 +25,7 @@ subprojects {
     }
 
     extra.apply {
-        set("creekVersion", "0.3.1-SNAPSHOT")
+        set("creekVersion", "0.3.1")
 
         set("spotBugsVersion", "4.7.3")         // https://mvnrepository.com/artifact/com.github.spotbugs/spotbugs-annotations
         set("classGraphVersion", "4.8.154")     // https://mvnrepository.com/artifact/io.github.classgraph/classgraph