Revert "misra.py: Fixed FN for rule 21.8"

This reverts commit 870b8b9c60.

addons/misra.py

@@ -3451,7 +3451,7 @@ class MisraChecker:
 
     def misra_21_8(self, data):
         for token in data.tokenlist:
-            if isFunctionCall(token) and (token.astOperand1.str in ('abort', 'exit', 'getenv', 'system')):
+            if isFunctionCall(token) and (token.astOperand1.str in ('abort', 'exit', 'getenv')):
                 self.reportError(token, 21, 8)
 
     def misra_21_9(self, data):

addons/test/misra/misra-test.c

@@ -1768,7 +1768,6 @@ static void misra_21_7(void) {
 static void misra_21_8(void) {
   abort(); // 21.8
   (void)getenv("foo"); // 21.8
-  (void)system("cmd"); // 21.8
   exit(-1); // 21.8
 }