Remove mitigations for incorrect node args

[compiler-errors]

This change https://github.com/rust-lang/rust/pull/118420/files#r1419874371 adds a missing write_args to properly record node args for lang-item calls.

Thus, in the unnecessary_to_owned lint, this ensures that the call_generic_args extracted by get_callee_generic_args_and_args are always correct, and we can remove the mitigation for #9504 and #10021 since the root cause has been fixed.

I'm not sure if there is other now-unnecessary code that can be removed, but this is the one I found when investigating #11965 (comment).

changelog: none

[rustbot]

r? @dswij

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[Jarcho]

Thanks for noticing this. If there are other cases they at least aren't harmful to have. @bors r+

[bors]

📌 Commit 3fceca2 has been approved by Jarcho

It is now in the queue for this repository.

[bors]

⌛ Testing commit 3fceca2 with merge 8b22471...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Jarcho
Pushing 8b22471 to master...