Revert "Explicitly set javaHome when the path to java is configured."

This reverts commit 2e2280f94fb3c8dec075acb74f31eadd6ff53a60.

Until we work out how to suppress sbt noise better.
-sbt-dev is 0.13.6-M2.
Stop using 'set every'.

Another in a long line of half-baked sbt settings which
overlaps confusingly with half a dozen others. Plus it's
dun broked.