tests: update needless_bool test stderr

[matthiaskrgr]

I'm getting a test failure otherwise with rust master (f688ba6).

changelog: none

[matthiaskrgr]

Looks like rust-lang/rust#61074 failed due to this

[phansch]

@bors r+ I will update the Rust PR once this is merged :)

[bors]

📌 Commit 3d0795b has been approved by phansch

[bors]

⌛ Testing commit 3d0795b with merge 9c85b02...

[bors]

☀️ Test successful - checks-travis, status-appveyor
Approved by: phansch
Pushing 9c85b02 to master...

[phansch]

Hmm in retrospect this change has broken that specific suggestion:

If

LL |       } else if returns_bool() {
   |  ____________^
LL | |         false
LL | |     } else {
LL | |         true
LL | |     };
   | |_____^ help: you can reduce it to: `!returns_bool()`

is applied, it results in:

if foo {
  // ...
} else !returns_bool()

I think that's because

rust-clippy/clippy_lints/src/needless_bool.rs

Line 72 in 5c1e30a

if parent_node_is_if_expr(&e, &cx) {

is not true anymore. I will take a look. (opened #4334)