Upgrade to Flyway 5.2.4

[jvalkeal]

Flyway 5.2.3 has a regression 2215 with mysql and this is supposedly fixed in 5.2.4 which were released this week. Got burned with this in dataflow when we started a work to upgrade to boot 2.1.x, so it'd be great to get this into snapshots.

[snicoll]

@jvalkeal thanks for letting us know. You'll get a 2.1.x snapshot with that version once this build completes.