After the jfx18 branch is forked from jfx, we need to change the release version to 19 in the master branch for OpenJFX 19.

We need to update the release values in the following files:

.jcheck/conf
build.properties

Additionally, since this bumps the major version we need to update the following unit test:

modules/javafx.base/src/test/java/test/com/sun/javafx/runtime/VersionInfoTest.java

See https://github.com/openjdk/jfx/blob/master/UPDATING-VERSION.md for details.