fix: apply lint fixes

Author: deandreamatias

example/lib/main.dart

@@ -15,7 +15,7 @@ import 'sources/signup_form.dart';
 void main() => runApp(const MyApp());
 
 class MyApp extends StatelessWidget {
-  const MyApp({Key? key}) : super(key: key);
+  const MyApp({super.key});
 
   @override
   Widget build(BuildContext context) {
@@ -37,7 +37,7 @@ class MyApp extends StatelessWidget {
 }
 
 class _HomePage extends StatelessWidget {
-  const _HomePage({Key? key}) : super(key: key);
+  const _HomePage();
 
   @override
   Widget build(BuildContext context) {

example/lib/sources/complete_form.dart

@@ -4,7 +4,7 @@ import 'package:form_builder_validators/form_builder_validators.dart';
 import 'package:intl/intl.dart';
 
 class CompleteForm extends StatefulWidget {
-  const CompleteForm({Key? key}) : super(key: key);
+  const CompleteForm({super.key});
 
   @override
   State<CompleteForm> createState() {

example/lib/sources/conditional_fields.dart

@@ -3,7 +3,7 @@ import 'package:flutter_form_builder/flutter_form_builder.dart';
 import 'package:form_builder_validators/form_builder_validators.dart';
 
 class ConditionalFields extends StatefulWidget {
-  const ConditionalFields({Key? key}) : super(key: key);
+  const ConditionalFields({super.key});
 
   @override
   State<ConditionalFields> createState() => _ConditionalFieldsState();

example/lib/sources/custom_fields.dart

@@ -2,7 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_form_builder/flutter_form_builder.dart';
 
 class CustomFields extends StatefulWidget {
-  const CustomFields({Key? key}) : super(key: key);
+  const CustomFields({super.key});
 
   @override
   State<CustomFields> createState() => _CustomFieldsState();

example/lib/sources/decorated_radio_checkbox.dart

@@ -3,7 +3,7 @@ import 'package:flutter_form_builder/flutter_form_builder.dart';
 
 /// Demonstrates the use of itemDecorators to wrap a box around selection items
 class DecoratedRadioCheckbox extends StatefulWidget {
-  const DecoratedRadioCheckbox({Key? key}) : super(key: key);
+  const DecoratedRadioCheckbox({super.key});
 
   @override
   State<DecoratedRadioCheckbox> createState() => _DecoratedRadioCheckboxState();

example/lib/sources/dynamic_fields.dart

@@ -7,7 +7,7 @@ import 'package:form_builder_validators/form_builder_validators.dart';
 /// fields that can be added to this widget. For the purposes of the widget, it
 /// is more than sufficient.
 class DynamicFields extends StatefulWidget {
-  const DynamicFields({Key? key}) : super(key: key);
+  const DynamicFields({super.key});
 
   @override
   State<DynamicFields> createState() => _DynamicFieldsState();

example/lib/sources/grouped_radio_checkbox.dart

@@ -3,7 +3,7 @@ import 'package:flutter_form_builder/flutter_form_builder.dart';
 import 'package:form_builder_validators/form_builder_validators.dart';
 
 class GroupedRadioCheckbox extends StatefulWidget {
-  const GroupedRadioCheckbox({Key? key}) : super(key: key);
+  const GroupedRadioCheckbox({super.key});
 
   @override
   State<GroupedRadioCheckbox> createState() {

example/lib/sources/related_fields.dart

@@ -2,7 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_form_builder/flutter_form_builder.dart';
 
 class RelatedFields extends StatefulWidget {
-  const RelatedFields({Key? key}) : super(key: key);
+  const RelatedFields({super.key});
 
   @override
   State<RelatedFields> createState() => _RelatedFieldsState();

example/lib/sources/signup_form.dart

@@ -3,7 +3,7 @@ import 'package:flutter_form_builder/flutter_form_builder.dart';
 import 'package:form_builder_validators/form_builder_validators.dart';
 
 class SignupForm extends StatefulWidget {
-  const SignupForm({Key? key}) : super(key: key);
+  const SignupForm({super.key});
 
   @override
   State<SignupForm> createState() => _SignupFormState();