Bump junit5 from 5.13.4 to 6.0.0 in /codegen (#575)

Bumps `junit5` from 5.13.4 to 6.0.0.

Updates `org.junit:junit-bom` from 5.13.4 to 6.0.0
- [Release notes](https://github.com/junit-team/junit-framework/releases)
- [Commits](junit-team/junit-framework@r5.13.4...r6.0.0)

Updates `org.junit.jupiter:junit-jupiter-api` from 5.13.4 to 6.0.0
- [Release notes](https://github.com/junit-team/junit-framework/releases)
- [Commits](junit-team/junit-framework@r5.13.4...r6.0.0)

Updates `org.junit.jupiter:junit-jupiter-engine` from 5.13.4 to 6.0.0
- [Release notes](https://github.com/junit-team/junit-framework/releases)
- [Commits](junit-team/junit-framework@r5.13.4...r6.0.0)

Updates `org.junit.jupiter:junit-jupiter-params` from 5.13.4 to 6.0.0
- [Release notes](https://github.com/junit-team/junit-framework/releases)
- [Commits](junit-team/junit-framework@r5.13.4...r6.0.0)

---
updated-dependencies:
- dependency-name: org.junit:junit-bom
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.junit.jupiter:junit-jupiter-api
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.junit.jupiter:junit-jupiter-engine
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.junit.jupiter:junit-jupiter-params
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

codegen/gradle/libs.versions.toml

@@ -1,5 +1,5 @@
 [versions]
-junit5 = "5.13.4"
+junit5 = "6.0.0"
 smithy = "1.62.0"
 test-logger-plugin = "4.0.0"
 spotbugs = "6.0.22"