[lld] Remove shadowing "size" field from classes that inherit from SyntheticSection (PR #166323)

[via llvm-commits]

Sterling-Augustine wrote:

I want to explicitly note here that github did not recommend maskray as a reviewer, but I added him as a courtesty regardless.

<img width="1272" height="308" alt="Screenshot 2025-11-03 at 11 18 13 PM" src="https://github.com/user-attachments/assets/f164f1d6-0ce8-4921-a3ce-e474a0a62731" />


https://github.com/llvm/llvm-project/pull/166323