Fixed name on system channel flags

[OldPranoy]

Summary

Corrected a name in System channel flags (SUPPRESS_JOIN_NOTIFICATION_REPLIES)

PR Type

• This PR improves the code (speed/style improvements or refactoring).
• [ X] This PR fixes an issue.
• This PR makes an addition to the library (new file, class, method, parameters, etc.).
• This PR makes a breaking change (renaming/removing parameters, methods, etc.).
• This PR doesn't make any code changes to the library (documentation, examples).

Checklist

• [X ] I have searched all pull requests for duplicates.
• [ X] I have tested the changes made.
  • I have properly changed the docs to reflect the changes made.
• If 'type: ignore' comments were used, a comment is left to explain why it is needed.