Firestore: Fix build warnings in FIRFirestore.mm and set_util.h (#9987)

Author: dconeybe

Firestore/Source/API/FIRFirestore.mm

@@ -340,7 +340,9 @@ void HandleFinalStatus(const Status &status) {
 
   int max_attempts = [FIRTransactionOptions defaultMaxAttempts];
   if (options) {
-    max_attempts = options.maxAttempts;
+    // Note: The cast of `maxAttempts` from `NSInteger` to `int` is safe (i.e. lossless) because
+    // `FIRTransactionOptions` does not allow values greater than `INT32_MAX` to be set.
+    max_attempts = static_cast<int>(options.maxAttempts);
   }
 
   _firestore->RunTransaction(std::move(internalUpdateBlock), std::move(objcTranslator),

Firestore/core/src/util/set_util.h

@@ -33,8 +33,8 @@ namespace util {
  *
  * The method runs in O(n) where n is the size of the two lists.
  *
- * @param before - The elements that exist in the original set.
- * @param after - The elements to diff against the original set.
+ * @param existing - The elements that exist in the original set.
+ * @param new_entries - The elements to diff against the original set.
  * @param comparator - The comparator for the elements in before and after.
  * @param on_add - A function to invoke for every element that is part of `
  * after` but not `before`.