Rollup merge of #40816 - estebank:issue-38321, r=nikomatsakis

Clarify suggetion for field used as method

Instead of

```rust
error: no method named `src_addr` found for type `&wire::ipv4::Repr` in the current scope
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^
    |
note: did you mean to write `self.src_addr`?
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^
```

present

```rust
error: no method named `src_addr` found for type `&wire::ipv4::Repr` in the current scope
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^ field, not a method
    |
    = help: did you mean to write `self.src_addr` instead of `self.src_addr(...)`?
```

Fix #38321.