Fix flakiness in ThreadingDiagnoserTests

Author: AndreyAkinshin

tests/BenchmarkDotNet.IntegrationTests/ThreadingDiagnoserTests.cs

@@ -155,8 +155,9 @@ private void AssertStats(Summary summary, Dictionary<string, (string metricName,
 
                 var metric = selectedReport.Metrics.Single(m => m.Key == assertion.Value.metricName);
 
-                // precision is set to 3 because CoreCLR might schedule some work item on it's own and hence affect the results..
-                Assert.Equal(assertion.Value.expectedValue, metric.Value.Value, precision: 3);
+                // precision is set to 2 because CoreCLR might schedule some work item on it's own and hence affect the results..
+                // precision = 3 is not enough (e.g., sometimes the actual value may be equal 1.0009765625 while the expected value is 1.0) 
+                Assert.Equal(assertion.Value.expectedValue, metric.Value.Value, precision: 2);
             }
         }
     }