Make a drop explicit to please clippy

```
warning: unused return value of `std::ffi::CString::from_raw` that must be used
    --> pcsc/src/lib.rs:1016:18
     |
1016 |         unsafe { CString::from_raw(self.inner.szReader as *mut c_char) };
     |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     |
     = note: call `drop(from_raw(ptr))` if you intend to drop the `CString`
     = note: `#[warn(unused_must_use)]` on by default
```

pcsc/src/lib.rs

@@ -1013,7 +1013,7 @@ impl ReaderState {
 impl Drop for ReaderState {
     fn drop(&mut self) {
         // Reclaim the name and drop it immediately.
-        unsafe { CString::from_raw(self.inner.szReader as *mut c_char) };
+        unsafe { drop(CString::from_raw(self.inner.szReader as *mut c_char)) };
     }
 }