Bump junit-jupiter-api from 5.7.2 to 5.8.0 in /samples/multiplatform

Bumps [junit-jupiter-api](https://github.com/junit-team/junit5) from 5.7.2 to 5.8.0.
- [Release notes](https://github.com/junit-team/junit5/releases)
- [Commits](https://github.com/junit-team/junit5/compare/r5.7.2...r5.8.0)

---
updated-dependencies:
- dependency-name: org.junit.jupiter:junit-jupiter-api
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

samples/multiplatform/build.gradle.kts

@@ -6,7 +6,7 @@ import org.gradle.api.tasks.testing.logging.TestExceptionFormat
 // for infix-api -> change to 'atrium-infix-en_GB'
 val atriumApi = "atrium-fluent-en_GB"
 val atriumVersion = "0.16.0"
-val junitVersion = "5.7.2"
+val junitVersion = "5.8.0"
 
 plugins {
     kotlin("multiplatform") version "1.5.30"