Fix: Last name - Privacy settings not working for forum the Display Name

[roopeshbuddyboss]

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Changes proposed in this Pull Request:

Fixes #2526 .

How to test the changes in this Pull Request:

1. Go to Setting->profile->Display Name Format->select "First name and Last name"
2. Now Go to front side User Edit Profile -> Change Lastname privacy "only me"
3. Login with other user and check the forum and see the previous changed user reply or discussion display name

Proof Screenshots or Video

https://www.loom.com/share/e188591291be405f8d1374e2a7dc8e2b

Other information:

• [x] Have you added an explanation of what your changes do and why you'd like us to include them?
• [ ] Have you written new tests for your changes, as applicable?
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