openmrs-core: replace log4j 1 which is EOL

Sounds like a plan!

As a side note @lluismf generally the master branches of modules work with much earlier versions of core. We are running, more or less, the latest releases (or even snapshots) of most of the reference app modules, plus some other modules, with OpenMRS 1.10.x. It’s rare that we have branches of modules targeted to certain versions of core. There’s limitations caused by maintaining this, of course, and there’s a chance we may have to change that in the future, but it would require some thought.

Take care, Mark