Do not warn about from_over_into with external crate types

[almindor]

Lint name: from_over_into

This lint should not be attempted on types that live in external crates. Right now it triggers e.g.:

impl Into<OutOfCrateType> for InCrateType {...}

I expected to see this happen:
Not to get this case linted as a warning because the OutOfCrateType is external and thus From cannot or might not be implementable on it since InCrateType is from this crate.

Instead, this happened:
It got linted as a warning.

Meta

• cargo clippy -V: clippy 0.1.51 (2fd73fa 2021-03-23)
• rustc -Vv:

rustc 1.51.0 (2fd73fabe 2021-03-23)
binary: rustc
commit-hash: 2fd73fabe469357a12c2c974c140f67e7cdd76d0
commit-date: 2021-03-23
host: x86_64-unknown-linux-gnu
release: 1.51.0
LLVM version: 11.0.1

[oribs1]

After a short research, the restriction was weakened in Rust 1.41.0 to allow these implementations:
https://blog.rust-lang.org/2020/01/30/Rust-1.41.0.html

So this lint is ok in the case of Into