This commit downgrades the maven failsafe plugin version. As of 2.19, the
generated jar is used for integration tests rather than the
`target/classes` directory. The fat jar in 1.4 has changed to move
classes to `BOOT-INF/classes` and therefore these are not found anymore.
There isn't a way to configure the jar file to use in the plugin. Users
willing to use the latest version should configure a `classifier` for the
repackaged jar so that the original jar is used by failsafe.
Closes gh-6254
6527aa0e80