use correct framework

[kasperk81]

the undocumented names (without period in dotnet 5+) can drop their support when move to double-digit (to avoid potential conflicts) https://learn.microsoft.com/en-us/dotnet/standard/frameworks#supported-target-frameworks

also unified a redundant reference

[kasperk81]

@cempehlivan i think test failure is not related to changes in this pr?

   Standard Output Messages:
 statu: Error
 message: Kartin son kullanma tarihi hatali.
 transactionId: 

in my fork it is failing on master as well due to some date miscalculation perhaps.