Modify rule S1172 Fix FP for Objective-C block definitions CPP-5916

rules/S1172/cfamily/rule.adoc

@@ -13,7 +13,7 @@ void f([[maybe_unused]] int i) {
 }
 ----
 
-In case of Objective-C, it is acceptable to have unused parameters if the method is supposed to be overridden.
+In case of Objective-C, it is acceptable to have unused parameters if the method is supposed to be overridden. Additionally, since Objective-C blocks don't allow unnamed parameters while they are typically used as callbacks, it is acceptable to have unused parameters in blocks.
 
 == How to fix it