M9-3-3: add testcase clarification note

Author: knewbury01

cpp/autosar/test/rules/M9-3-3/test.cpp

@@ -210,6 +210,7 @@ class Z4 {
 };
 
 void fp_reported_in_381() {
+  // added to test template initialization effects/lack thereof
   Z4 z;
   int i = z.front();
   z.fill(i);