Rollup merge of #131669 - niacdoial:linting-ptrdyn-ffi, r=workingjubilee

lint: change help for pointers to dyn types in FFI

### Context
while playing around, I encountered the warning for dyn types in `extern "C"` functions, but even after that I assumed that a (rust) raw pointer could be interpreted in C ('s ABI) as a `void *`... to be fair part of why I ignored the warning is because I wanted to poke at the generated assembly, not make useful code.

### Example

```rust
extern "C"
fn caller(callee: *const dyn Fn(i32)->i32){
    // -- snip --
}
```

old warning:
```
warning: `extern` fn uses type `dyn Fn(i32) -> i32`, which is not FFI-safe
 --> file/name.rs:42:19
   |
42 | fn caller(callee: *const dyn Fn(i32)->i32) {
   |                   ^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
   |
  = note: trait objects have no C equivalent
  = note: `#[warn(improper_ctypes_definitions)]` on by default
  ```

new warning:
```
warning: `extern` fn uses type `dyn Fn(i32) -> i32`, which is not FFI-safe
 --> file/name.rs:42:19
   |
42 | fn caller(callee: *const dyn Fn(i32)->i32) -> (){
   |                   ^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
   |
  = note: this pointer to an unsized type contains metadata, which makes it incompatible with a C pointer
  = note: `#[warn(improper_ctypes_definitions)]` on by default
```

0 files changed, 0 insertions, 0 deletions