[Kinetics] Implement band aid for plog validations

The previous set of temperatures used for validation of P-log rates
is a somewhat arbitrary set. Some mechanisms fail for 200 K but
work fine for 300 K and up. Work-around discussed in Cantera#1405.

src/kinetics/PlogRate.cpp

@@ -133,7 +133,7 @@ void PlogRate::validate(const std::string& equation, const Kinetics& kin)
     }
 
     fmt::memory_buffer err_reactions;
-    double T[] = {200.0, 500.0, 1000.0, 2000.0, 5000.0, 10000.0};
+    double T[] = {300.0, 500.0, 1000.0, 2000.0, 5000.0, 10000.0};
     PlogData data;
 
     for (auto iter = ++pressures_.begin(); iter->first < 1000; iter++) {