Removed ignore from concurrent index access test case.
Removed ignore from concurrent index access test case.

laimis/lucenenet,NightOwl888/lucenenet,apache/lucenenet,apache/lucenenet,NightOwl888/lucenenet,sisve/lucenenet,jeme/lucenenet,apache/lucenenet,jeme/lucenenet,apache/lucenenet,NightOwl888/lucenenet,jeme/lucenenet,sisve/lucenenet,jeme/lucenenet,NightOwl888/lucenenet,laimis/lucenenet