Fix weird interaction between maven-release, maven-enforcer and RAT plugins

While trying to make the 1.5.0 release I ran into a bizarre failure from RAT complaining about a file it should have been ignoring according to the plugin configuration.

Disabling the newly added maven-enforcer plugin "fixed" the issue, but we need to keep this in the build to make sure new dependencies don't creep into the JDBC driver that is supposed to be as small as possible.

For the sake of the release the jdbc-all jar's size was checked manually.