uninit_assumed_init lint does not recognize trivial misuse

[Shnatsel]

uninit_assumed_init lint (see #4272) correctly recognizes the following anti-pattern:

unsafe { let mut x = MaybeUninit::<&i32>::uninit().assume_init(); }

However, it does not recognize a slightly altered version of it:

    let mut x = MaybeUninit::<&i32>::uninit();
    let x = unsafe { x.assume_init() };

Clippy version: clippy 0.0.212 (c8e3cfb 2019-10-28)