Bump flywayVersion from 10.20.1 to 10.21.0 (#252)

Bumps `flywayVersion` from 10.20.1 to 10.21.0.

Updates `org.flywaydb:flyway-core` from 10.20.1 to 10.21.0
- [Release notes](https://github.com/flyway/flyway/releases)
- [Commits](flyway/flyway@flyway-10.20.1...flyway-10.21.0)

Updates `org.flywaydb:flyway-database-postgresql` from 10.20.1 to 10.21.0

---
updated-dependencies:
- dependency-name: org.flywaydb:flyway-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.flywaydb:flyway-database-postgresql
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

build.gradle.kts

@@ -21,7 +21,7 @@ val kotlinVersion = "1.9.24"
 val mockkVersion = "1.13.13"
 val postgresVersion = "42.7.4"
 val hikariVersion = "5.1.0"
-val flywayVersion = "10.20.1"
+val flywayVersion = "10.21.0"
 val gsonVersion = "2.11.0"
 val kafkaVersion = "3.7.0"
 val altinnKanalSchemasVersion = "2.0.0"