[clang] [clang-tools-extra] [clang][CodeComplete] skip explicit obj param in SignatureHelp (PR #146649)

[Mythreya Kuricheti via cfe-commits]

MythreyaK wrote:

Seems to be working as expected. I'll add a test case for this as well. 

![image](https://github.com/user-attachments/assets/f736c68f-a64d-4af6-876a-d647d0d6541e)
![image](https://github.com/user-attachments/assets/e40ee898-a161-4564-869c-b566e7b3452b)


https://github.com/llvm/llvm-project/pull/146649