remove target override for bindgen because it isn't necessary

[HackerFoo]

This fixes an issue where aarch64-apple-ios-sim won't build with the error:

unable to generate bindings: ClangDiagnostic("error: version 'sim' in target triple 'aarch64-apple-ios-sim' is invalid\n")

I have a fix for bindgen, but the workaround in build.rs makes this ineffective.

[simlay]

So, this seems perfect, correct and builds on my xcode 16.0 without the errors shown in the rust-bindgen PR. The part that's unclear to me is if it works as expected with older versions of clang/xcode.

Admittedly, there's not a policy of "oldest xcode supported" on this project but I'm anxious about broken builds for people on xcode 15 or something.

[madsmtm]

Ideally, we'd wait for rust-lang/rust-bindgen#3182 to land, and then add a dependency on the specific patch version that's released in. Then bindgen itself would be passing arm64-*, and older Xcode versions would still be supported.