Fix acceptance test heap size to 128m

Buck defaults to running 1.25 * ncpus tests in parallel.  If each test
uses a heap size of 128M then an 8 core system will need at least
1.25G of RAM for JVM heap during test execution.  The actual memory
used will of course be much higher due to JVM overhead.

Set a default memory for acceptance tests to prevent a huge explosion
during `buck test --all`.

Change-Id: I373df822c029d2dc24c625129f540211cda910e7

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/git/BUCK

@@ -3,13 +3,11 @@ include_defs('//gerrit-acceptance-tests/tests.defs')
 acceptance_tests(
   srcs = ['SubmitOnPushIT.java'],
   deps = [':util'],
-  vm_args = ['-Xmx512m'],
 )
 
 acceptance_tests(
   srcs = ['HttpPushForReviewIT.java', 'SshPushForReviewIT.java'],
   deps = [':push_for_review'],
-  vm_args = ['-Xmx512m'],
 )
 
 java_library(