loosen threshold (#5180)

Author: Jeffrey Mendelsohn

groups/bsl/bslmt/bslmt_throughputbenchmark.t.cpp

@@ -652,7 +652,7 @@ int main(int argc, char *argv[])
             }
 
             ASSERTV(countTightBoundPassed,
-                    100 * countTightBoundPassed >= 50 * k_NUM_TRIALS);
+                    100 * countTightBoundPassed >= 35 * k_NUM_TRIALS);
 
             ASSERTV(countLooseBoundPassed,
                     100 * countLooseBoundPassed >= 60 * k_NUM_TRIALS);