fixed typo

Author: MauScheff

packages/in_app_purchase/ios/Classes/InAppPurchasePlugin.m

@@ -187,7 +187,7 @@ - (void)addPayment:(FlutterMethodCall *)call result:(FlutterResult)result {
     result([FlutterError
         errorWithCode:@"storekit_duplicate_product_object"
               message:@"There is a pending transaction for the same product identifier. Please "
-                      @"either wait for it to be finished or finish it manuelly using "
+                      @"either wait for it to be finished or finish it manually using "
                       @"`completePurchase` to avoid edge cases."
 
               details:call.arguments]);

packages/in_app_purchase/ios/Tests/InAppPurchasePluginTest.m

@@ -145,7 +145,7 @@ - (void)testAddPaymentWithSameProductIDWillFail {
                     XCTAssertEqualObjects(
                         error.message,
                         @"There is a pending transaction for the same product identifier. Please "
-                        @"either wait for it to be finished or finish it manuelly using "
+                        @"either wait for it to be finished or finish it manually using "
                         @"`completePurchase` to avoid edge cases.");
                     [expectation fulfill];
                   }];