[clangd] fix wrong CalleeArgInfo in the hover

```
void foobar(int);
int main() {
  foobar(1 + 2);
           ^
}
```

Currently the CalleeArgInfo will be "Passed by reference", which should
be "Passed by value".

Fixes https://github.com/clangd/clangd/issues/1467

Differential Revision: https://reviews.llvm.org/D142014