Make run test 572-checker-array-get-regression gcstress friendly.

The large array allocated in
test/572-checker-array-get-regression/src/Main.java used to
be too big for the small heap used in gcstress mode.  Use a
smaller array size that however still exercises the initial
issue checked by this regression test.

Bug: 26817006
Bug: 12687968
Change-Id: Id7080a18007cad9b5d4ac31b45f7df46213a908e