azure-pipelines.yml: Increased maximumParallelJobs on net451 from 7 to 8
azure-pipelines.yml: Increased maximumParallelJobs on net451 from 7 to 8

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