Auto merge of #102783 - RalfJung:tls, r=thomcc

sync thread_local key conditions exactly with what the macro uses

This makes the `cfg` in `mod.rs` syntactically the same as those in `local.rs`.

I don't think this should actually change anything, but seems better to be consistent?
I looked into this due to rust-lang/rust#102549, but this PR would make it *less* likely that `__OsLocalKeyInner` is going to get provided, so this cannot help with that issue.

r? `@thomcc`