Reduce number of parallel builds in ParallelBuildChainTest #825

The test case
testIndividualProjectBuilds_WithManyProjects_ProjectRelaxedRule() in
ParallelBuildChainTest fails randomly (in I-Builds) because not all jobs
that are supposed to run build operations are scheduled and started in
time. Since the test is not supposed to validate that a specific number
of jobs can be started, the number of jobs/builds to be spawned must
actually not be as high as currently defined. This change reduces the
number of projects in the test case to avoid random test failures while
keeping expressiveness of the test case.

Fixes #825

resources/tests/org.eclipse.core.tests.resources/src/org/eclipse/core/tests/internal/builders/ParallelBuildChainTest.java

@@ -144,7 +144,7 @@ public void testIndividualProjectBuilds_ProjectRelaxedRule() throws Exception {
 
 	@Test
 	public void testIndividualProjectBuilds_WithManyProjects_ProjectRelaxedRule() throws Exception {
-		int numberOfParallelBuilds = 30;
+		int numberOfParallelBuilds = 15;
 		var longRunningProjects = createMultipleTestProjects(numberOfParallelBuilds, BuildDurationType.LONG_RUNNING,
 				RuleType.CURRENT_PROJECT_RELAXED);
 		executeIndividualFullProjectBuilds(numberOfParallelBuilds, () -> {