/usr/share/java/openjfx/jre/lib/javafx.properties is in libopenjfx-java 8u161-b12-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | javafx.runtime.version=8.0.161
javafx.runtime.build=b00
|