revert flutter_secure_storage back to v5.1.2

pubspec.lock

@@ -173,7 +173,7 @@ packages:
       name: flutter_secure_storage
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "6.0.0"
+    version: "5.1.2"
   flutter_secure_storage_linux:
     dependency: transitive
     description:

pubspec.yaml

@@ -34,7 +34,7 @@ dependencies:
   # The following adds the Cupertino Icons font to your application.
   # Use with the CupertinoIcons class for iOS style icons.
   cupertino_icons: ^1.0.2
-  flutter_secure_storage: ^6.0.0
+  flutter_secure_storage: ^5.1.2
   logger: ^1.1.0
   http: ^0.13.4
   flutter_staggered_grid_view: ^0.6.1