Write tests for view pinned_post_screen.dart

[palisadoes]

The Talawa code base needs to be 100% reliable. This means we need to have 100% unittest code coverage.

We will need unittests done for all methods, classes and functions found in this file.

Any widgets referenced in this file must also have unittests done

lib/views/after_auth_screens/feed/pinned_post_screen.dart

PR Acceptance Criteria

• When complete this file must show 100% coverage when merged into the code base.
• The current code coverage for this file can be found here:
  • https://app.codecov.io/gh/PalisadoesFoundation/talawa?displayType=list
• The PR will show a report for the code coverage for the file you have added. You can use that as a guide

[imshivam-gupta]

@palisadoes @noman2002 Can you please assign this issue to me