Auto merge of #1871 - hyd-dev:no-mangle-method, r=RalfJung

Auto merge of #1871 - hyd-dev:no-mangle-method, r=RalfJung

Update tests for `#[no_mangle]` on associated functions

https://github.com/rust-lang/rust/pull/86492 has landed:
- The code in https://github.com/rust-lang/miri/issues/1837 starts to work (even without `AssocFn::foo();` at line 12) in Miri.
- `pub` is not necessary for `#[no_mangle]` associated functions in `test-cargo-miri/exported-symbol-dep/src/lib.rs` anymore.

Closes https://github.com/rust-lang/miri/issues/1837.