Declare to heap that switching from zygote to its child in test 2031

Otherwise userfaultfd GC logic asserts in certain cases that we are
zygote, whereas that's not true as per the runtime.

Test: art/test/testrunner/testrunner.py --host -t 2031
Change-Id: Ice5dc3605ac8623dfb139773aff7cc7c8b6116ce
1 file changed