adjust declared types to work with dart 2 typing at runtime (#19007)

* adjust declared types to work with dart 2 typing at runtime

* review comments

* update packages/flutter_tools/lib/src/ios/simulators.dart

packages/flutter_tools/lib/src/version.dart

diff --git a/packages/flutter_tools/lib/src/version.dart b/packages/flutter_tools/lib/src/version.dart
index c08c444..6947a27 100644
--- a/packages/flutter_tools/lib/src/version.dart
+++ b/packages/flutter_tools/lib/src/version.dart
@@ -388,7 +388,7 @@
     return const VersionCheckStamp();
   }
 
-  static VersionCheckStamp fromJson(Map<String, String> jsonObject) {
+  static VersionCheckStamp fromJson(Map<String, dynamic> jsonObject) {
     DateTime readDateTime(String property) {
       return jsonObject.containsKey(property)
           ? DateTime.parse(jsonObject[property])