Down forked JVM heap size from 2800m to 2200m for jdk8 and jdk11

Docker container we run tests in is hardcoded 20G. Our fork count is 0.25C currently. The jenkins machines are 16CPUs. 0.25C means 4CPUs so 4 forks running at any one time. Our current forked JVM heap size is 2800m if jdk8 or 3200m if jdk11. If we want to move our fork count to 0.5C, then that means 8 forks possibly running at once: i.e. 8 * 2800 = 22.4G... i.e. too big for the container. This issue is about running w/ smaller forked jvm heap size. If 2200m then, its 19.6G which is cutting it close but might allow us sqeeze through (mvn takes 4G!). Lets see.