Regression in `useless_transmute` due to rustup

[flip1995]

After rust-lang/rust#69189, the following check returns true for types, where only the lifetimes differ: &'a T == &'b T

rust-clippy/clippy_lints/src/transmute.rs

Lines 303 to 307 in c036c4f

	let from_ty = cx.tables.expr_ty(&args[0]);
	let to_ty = cx.tables.expr_ty(e);
	match (&from_ty.kind, &to_ty.kind) {
	_ if from_ty == to_ty => span_lint(

According to rust-lang/rust#69189 (comment), this probably needs to be fixed by checking the lifetimes of the types with MIR borrowck.

Originally posted by @flip1995 in #5333

[dtolnay]

👍 this was picked up in miniserde's build. https://travis-ci.org/github/dtolnay/miniserde/jobs/665845514

If this may take a while to fix, could you please consider making useless_transmute allow-by-default for now?

[flip1995]

Yes, I also thought about this, but wanted to wait until someone complains. 😄 I'll move it to nursery,